I did a clean install on Linux mint, as I bought a new PC around christmas.
If I look at: Project Manager / Preferences / Configure Paths, then I see (among other things) an KICAD6_SYMBOL_DIR which is set to /usr/share/kicad/symbols/
Note that you do not have the 6 in your path variable, there obviously is some mixup between KiCad V5 and V6 on your system.
Just for completeness, Project Manager / Preferences / Manage Symbol Libraries also has the 6 on my system, and it wants *.kicad_sym files.
And the libraries themselves are also installed on my system:
paul@cezanne:/usr/share/kicad/symbols$ ls -hl
total 102M
-rw-r--r-- 1 root root 369K Dec 23 15:25 4xxx_IEEE.kicad_sym
-rw-r--r-- 1 root root 297K Dec 23 15:25 4xxx.kicad_sym
-rw-r--r-- 1 root root 277K Dec 23 15:25 74xGxx.kicad_sym
-rw-r--r-- 1 root root 677K Dec 23 15:25 74xx_IEEE.kicad_sym
-rw-r--r-- 1 root root 941K Dec 23 15:25 74xx.kicad_sym
-rw-r--r-- 1 root root 338K Dec 23 15:25 Amplifier_Audio.kicad_sym
-rw-r--r-- 1 root root 19K Dec 23 15:25 Amplifier_Buffer.kicad_sym
-rw-r--r-- 1 root root 131K Dec 23 15:25 Amplifier_Current.kicad_sym
-rw-r--r-- 1 root root 44K Dec 23 15:25 Amplifier_Difference.kicad_sym
-rw-r--r-- 1 root root 62K Dec 23 15:25 Amplifier_Instrumentation.kicad_sym
-rw-r--r-- 1 root root 550K Dec 23 15:25 Amplifier_Operational.kicad_sym
-rw-r--r-- 1 root root 9,6K Dec 23 15:25 Amplifier_Video.kicad_sym
-rw-r--r-- 1 root root 512K Dec 23 15:25 Analog_ADC.kicad_sym
-rw-r--r-- 1 root root 345K Dec 23 15:25 Analog_DAC.kicad_sym
-rw-r--r-- 1 root root 81K Dec 23 15:25 Analog.kicad_sym
-rw-r--r-- 1 root root 902K Dec 23 15:25 Analog_Switch.kicad_sym
-rw-r--r-- 1 root root 404K Dec 23 15:25 Audio.kicad_sym
-rw-r--r-- 1 root root 358K Dec 23 15:25 Battery_Management.kicad_sym
-rw-r--r-- 1 root root 4,3K Dec 23 15:25 Buffer.kicad_sym
-rw-r--r-- 1 root root 146K Dec 23 15:25 Comparator.kicad_sym
-rw-r--r-- 1 root root 3,7M Dec 23 15:25 Connector_Generic.kicad_sym
-rw-r--r-- 1 root root 3,8M Dec 23 15:25 Connector_Generic_MountingPin.kicad_sym
-rw-r--r-- 1 root root 3,8M Dec 23 15:25 Connector_Generic_Shielded.kicad_sym
-rw-r--r-- 1 root root 3,1M Dec 23 15:25 Connector.kicad_sym
-rw-r--r-- 1 root root 197K Dec 23 15:25 Converter_ACDC.kicad_sym
-rw-r--r-- 1 root root 658K Dec 23 15:25 Converter_DCDC.kicad_sym
-rw-r--r-- 1 root root 616K Dec 23 15:25 CPLD_Altera.kicad_sym
-rw-r--r-- 1 root root 16K Dec 23 15:25 CPLD_Microchip.kicad_sym
-rw-r--r-- 1 root root 221K Dec 23 15:25 CPLD_Xilinx.kicad_sym
-rw-r--r-- 1 root root 247K Dec 23 15:25 CPU.kicad_sym
-rw-r--r-- 1 root root 60K Dec 23 15:25 CPU_NXP_68000.kicad_sym
-rw-r--r-- 1 root root 40K Dec 23 15:25 CPU_NXP_6800.kicad_sym
-rw-r--r-- 1 root root 261K Dec 23 15:25 CPU_NXP_IMX.kicad_sym
-rw-r--r-- 1 root root 193K Dec 23 15:25 CPU_PowerPC.kicad_sym
-rw-r--r-- 1 root root 2,2M Dec 23 15:25 Device.kicad_sym
-rw-r--r-- 1 root root 200K Dec 23 15:25 Diode_Bridge.kicad_sym
-rw-r--r-- 1 root root 620K Dec 23 15:25 Diode.kicad_sym
-rw-r--r-- 1 root root 18K Dec 23 15:25 Diode_Laser.kicad_sym
-rw-r--r-- 1 root root 605K Dec 23 15:25 Display_Character.kicad_sym
-rw-r--r-- 1 root root 144K Dec 23 15:25 Display_Graphic.kicad_sym
-rw-r--r-- 1 root root 46K Dec 23 15:25 Driver_Display.kicad_sym
-rw-r--r-- 1 root root 469K Dec 23 15:25 Driver_FET.kicad_sym
-rw-r--r-- 1 root root 7,2K Dec 23 15:25 Driver_Haptic.kicad_sym
-rw-r--r-- 1 root root 351K Dec 23 15:25 Driver_LED.kicad_sym
-rw-r--r-- 1 root root 291K Dec 23 15:25 Driver_Motor.kicad_sym
-rw-r--r-- 1 root root 23K Dec 23 15:25 Driver_Relay.kicad_sym
-rw-r--r-- 1 root root 7,3K Dec 23 15:25 Driver_TEC.kicad_sym
-rw-r--r-- 1 root root 28K Dec 23 15:25 DSP_AnalogDevices.kicad_sym
-rw-r--r-- 1 root root 41K Dec 23 15:25 DSP_Freescale.kicad_sym
-rw-r--r-- 1 root root 160K Dec 23 15:25 DSP_Microchip_DSPIC33.kicad_sym
-rw-r--r-- 1 root root 38K Dec 23 15:25 DSP_Motorola.kicad_sym
-rw-r--r-- 1 root root 20K Dec 23 15:25 DSP_Texas.kicad_sym
-rw-r--r-- 1 root root 7,2K Dec 23 15:25 Fiber_Optic.kicad_sym
-rw-r--r-- 1 root root 77K Dec 23 15:25 Filter.kicad_sym
-rw-r--r-- 1 root root 560K Dec 23 15:25 FPGA_Lattice.kicad_sym
-rw-r--r-- 1 root root 474K Dec 23 15:25 FPGA_Microsemi.kicad_sym
-rw-r--r-- 1 root root 2,1M Dec 23 15:25 FPGA_Xilinx_Artix7.kicad_sym
-rw-r--r-- 1 root root 948K Dec 23 15:25 FPGA_Xilinx.kicad_sym
-rw-r--r-- 1 root root 2,7M Dec 23 15:25 FPGA_Xilinx_Kintex7.kicad_sym
-rw-r--r-- 1 root root 3,7M Dec 23 15:25 FPGA_Xilinx_Spartan6.kicad_sym
-rw-r--r-- 1 root root 8,0M Dec 23 15:25 FPGA_Xilinx_Virtex5.kicad_sym
-rw-r--r-- 1 root root 6,7M Dec 23 15:25 FPGA_Xilinx_Virtex6.kicad_sym
-rw-r--r-- 1 root root 9,1M Dec 23 15:25 FPGA_Xilinx_Virtex7.kicad_sym
-rw-r--r-- 1 root root 11K Dec 23 15:25 GPU.kicad_sym
-rw-r--r-- 1 root root 79K Dec 23 15:25 Graphic.kicad_sym
-rw-r--r-- 1 root root 229K Dec 23 15:25 Interface_CAN_LIN.kicad_sym
-rw-r--r-- 1 root root 6,8K Dec 23 15:25 Interface_CurrentLoop.kicad_sym
-rw-r--r-- 1 root root 226K Dec 23 15:25 Interface_Ethernet.kicad_sym
-rw-r--r-- 1 root root 274K Dec 23 15:25 Interface_Expansion.kicad_sym
-rw-r--r-- 1 root root 21K Dec 23 15:25 Interface_HDMI.kicad_sym
-rw-r--r-- 1 root root 23K Dec 23 15:25 Interface_HID.kicad_sym
-rw-r--r-- 1 root root 566K Dec 23 15:25 Interface.kicad_sym
-rw-r--r-- 1 root root 55K Dec 23 15:25 Interface_LineDriver.kicad_sym
-rw-r--r-- 1 root root 108K Dec 23 15:25 Interface_Optical.kicad_sym
-rw-r--r-- 1 root root 16K Dec 23 15:25 Interface_Telecom.kicad_sym
-rw-r--r-- 1 root root 475K Dec 23 15:25 Interface_UART.kicad_sym
-rw-r--r-- 1 root root 450K Dec 23 15:25 Interface_USB.kicad_sym
-rw-r--r-- 1 root root 30K Dec 23 15:25 Isolator_Analog.kicad_sym
-rw-r--r-- 1 root root 1,3M Dec 23 15:25 Isolator.kicad_sym
-rw-r--r-- 1 root root 23K Dec 23 15:25 Jumper.kicad_sym
-rw-r--r-- 1 root root 256K Dec 23 15:25 LED.kicad_sym
-rw-r--r-- 1 root root 177K Dec 23 15:25 Logic_LevelTranslator.kicad_sym
-rw-r--r-- 1 root root 30K Dec 23 15:25 Logic_Programmable.kicad_sym
-rw-r--r-- 1 root root 11K Dec 23 15:25 MCU_AnalogDevices.kicad_sym
-rw-r--r-- 1 root root 115K Dec 23 15:25 MCU_Cypress.kicad_sym
-rw-r--r-- 1 root root 18K Dec 23 15:25 MCU_Dialog.kicad_sym
-rw-r--r-- 1 root root 7,2K Dec 23 15:25 MCU_Espressif.kicad_sym
-rw-r--r-- 1 root root 167K Dec 23 15:25 MCU_Intel.kicad_sym
-rw-r--r-- 1 root root 20K Dec 23 15:25 MCU_Microchip_8051.kicad_sym
-rw-r--r-- 1 root root 1,5M Dec 23 15:25 MCU_Microchip_ATmega.kicad_sym
-rw-r--r-- 1 root root 439K Dec 23 15:25 MCU_Microchip_ATtiny.kicad_sym
-rw-r--r-- 1 root root 89K Dec 23 15:25 MCU_Microchip_AVR.kicad_sym
-rw-r--r-- 1 root root 39K Dec 23 15:25 MCU_Microchip_PIC10.kicad_sym
-rw-r--r-- 1 root root 160K Dec 23 15:25 MCU_Microchip_PIC12.kicad_sym
-rw-r--r-- 1 root root 923K Dec 23 15:25 MCU_Microchip_PIC16.kicad_sym
-rw-r--r-- 1 root root 524K Dec 23 15:25 MCU_Microchip_PIC18.kicad_sym
-rw-r--r-- 1 root root 53K Dec 23 15:25 MCU_Microchip_PIC24.kicad_sym
-rw-r--r-- 1 root root 106K Dec 23 15:25 MCU_Microchip_PIC32.kicad_sym
-rw-r--r-- 1 root root 39K Dec 23 15:25 MCU_Microchip_SAMA.kicad_sym
-rw-r--r-- 1 root root 216K Dec 23 15:25 MCU_Microchip_SAMD.kicad_sym
-rw-r--r-- 1 root root 115K Dec 23 15:25 MCU_Microchip_SAME.kicad_sym
-rw-r--r-- 1 root root 73K Dec 23 15:25 MCU_Microchip_SAML.kicad_sym
-rw-r--r-- 1 root root 30K Dec 23 15:25 MCU_Microchip_SAMV.kicad_sym
-rw-r--r-- 1 root root 532K Dec 23 15:25 MCU_Module.kicad_sym
-rw-r--r-- 1 root root 68K Dec 23 15:25 MCU_Nordic.kicad_sym
-rw-r--r-- 1 root root 163K Dec 23 15:25 MCU_NXP_ColdFire.kicad_sym
-rw-r--r-- 1 root root 68K Dec 23 15:25 MCU_NXP_HC11.kicad_sym
-rw-r--r-- 1 root root 37K Dec 23 15:25 MCU_NXP_HC12.kicad_sym
-rw-r--r-- 1 root root 22K Dec 23 15:25 MCU_NXP_HCS12.kicad_sym
-rw-r--r-- 1 root root 890K Dec 23 15:25 MCU_NXP_Kinetis.kicad_sym
-rw-r--r-- 1 root root 226K Dec 23 15:25 MCU_NXP_LPC.kicad_sym
-rw-r--r-- 1 root root 56K Dec 23 15:25 MCU_NXP_MAC7100.kicad_sym
-rw-r--r-- 1 root root 19K Dec 23 15:25 MCU_NXP_MCore.kicad_sym
-rw-r--r-- 1 root root 5,7K Dec 23 15:25 MCU_NXP_NTAG.kicad_sym
-rw-r--r-- 1 root root 527K Dec 23 15:25 MCU_NXP_S08.kicad_sym
-rw-r--r-- 1 root root 28K Dec 23 15:25 MCU_Parallax.kicad_sym
-rw-r--r-- 1 root root 11K Dec 23 15:25 MCU_Renesas_Synergy_S1.kicad_sym
-rw-r--r-- 1 root root 103K Dec 23 15:25 MCU_SiFive.kicad_sym
-rw-r--r-- 1 root root 113K Dec 23 15:25 MCU_SiliconLabs.kicad_sym
-rw-r--r-- 1 root root 9,5K Dec 23 15:25 MCU_STC.kicad_sym
-rw-r--r-- 1 root root 960K Dec 23 15:25 MCU_ST_STM32F0.kicad_sym
-rw-r--r-- 1 root root 954K Dec 23 15:25 MCU_ST_STM32F1.kicad_sym
-rw-r--r-- 1 root root 410K Dec 23 15:25 MCU_ST_STM32F2.kicad_sym
-rw-r--r-- 1 root root 751K Dec 23 15:25 MCU_ST_STM32F3.kicad_sym
-rw-r--r-- 1 root root 2,9M Dec 23 15:25 MCU_ST_STM32F4.kicad_sym
-rw-r--r-- 1 root root 2,4M Dec 23 15:25 MCU_ST_STM32F7.kicad_sym
-rw-r--r-- 1 root root 15K Dec 23 15:25 MCU_ST_STM32G0.kicad_sym
-rw-r--r-- 1 root root 410K Dec 23 15:25 MCU_ST_STM32H7.kicad_sym
-rw-r--r-- 1 root root 1020K Dec 23 15:25 MCU_ST_STM32L0.kicad_sym
-rw-r--r-- 1 root root 1,5M Dec 23 15:25 MCU_ST_STM32L1.kicad_sym
-rw-r--r-- 1 root root 1,4M Dec 23 15:25 MCU_ST_STM32L4.kicad_sym
-rw-r--r-- 1 root root 718K Dec 23 15:25 MCU_ST_STM32L4+.kicad_sym
-rw-r--r-- 1 root root 180K Dec 23 15:25 MCU_ST_STM8.kicad_sym
-rw-r--r-- 1 root root 132K Dec 23 15:25 MCU_Texas.kicad_sym
-rw-r--r-- 1 root root 1,2M Dec 23 15:25 MCU_Texas_MSP430.kicad_sym
-rw-r--r-- 1 root root 11K Dec 23 15:25 MCU_Texas_SimpleLink.kicad_sym
-rw-r--r-- 1 root root 25K Dec 23 15:25 Mechanical.kicad_sym
-rw-r--r-- 1 root root 139K Dec 23 15:25 Memory_EEPROM.kicad_sym
-rw-r--r-- 1 root root 60K Dec 23 15:25 Memory_EPROM.kicad_sym
-rw-r--r-- 1 root root 134K Dec 23 15:25 Memory_Flash.kicad_sym
-rw-r--r-- 1 root root 35K Dec 23 15:25 Memory_NVRAM.kicad_sym
-rw-r--r-- 1 root root 304K Dec 23 15:25 Memory_RAM.kicad_sym
-rw-r--r-- 1 root root 12K Dec 23 15:25 Memory_ROM.kicad_sym
-rw-r--r-- 1 root root 4,1K Dec 23 15:25 Memory_UniqueID.kicad_sym
-rw-r--r-- 1 root root 56K Dec 23 15:25 Motor.kicad_sym
-rw-r--r-- 1 root root 196K Dec 23 15:25 Oscillator.kicad_sym
-rw-r--r-- 1 root root 177K Dec 23 15:25 Potentiometer_Digital.kicad_sym
-rw-r--r-- 1 root root 145K Dec 23 15:25 power.kicad_sym
-rw-r--r-- 1 root root 518K Dec 23 15:25 Power_Management.kicad_sym
-rw-r--r-- 1 root root 343K Dec 23 15:25 Power_Protection.kicad_sym
-rw-r--r-- 1 root root 125K Dec 23 15:25 Power_Supervisor.kicad_sym
-rw-r--r-- 1 root root 33K Dec 23 15:25 pspice.kicad_sym
-rw-r--r-- 1 root root 44K Dec 23 15:25 Reference_Current.kicad_sym
-rw-r--r-- 1 root root 334K Dec 23 15:25 Reference_Voltage.kicad_sym
-rw-r--r-- 1 root root 329K Dec 23 15:25 Regulator_Controller.kicad_sym
-rw-r--r-- 1 root root 2,7K Dec 23 15:25 Regulator_Current.kicad_sym
-rw-r--r-- 1 root root 1,7M Dec 23 15:25 Regulator_Linear.kicad_sym
-rw-r--r-- 1 root root 43K Dec 23 15:25 Regulator_SwitchedCapacitor.kicad_sym
-rw-r--r-- 1 root root 1,7M Dec 23 15:25 Regulator_Switching.kicad_sym
-rw-r--r-- 1 root root 624K Dec 23 15:25 Relay.kicad_sym
-rw-r--r-- 1 root root 231K Dec 23 15:25 Relay_SolidState.kicad_sym
-rw-r--r-- 1 root root 63K Dec 23 15:25 RF_AM_FM.kicad_sym
-rw-r--r-- 1 root root 90K Dec 23 15:25 RF_Amplifier.kicad_sym
-rw-r--r-- 1 root root 80K Dec 23 15:25 RF_Bluetooth.kicad_sym
-rw-r--r-- 1 root root 236K Dec 23 15:25 RF_Filter.kicad_sym
-rw-r--r-- 1 root root 83K Dec 23 15:25 RF_GPS.kicad_sym
-rw-r--r-- 1 root root 91K Dec 23 15:25 RF_GSM.kicad_sym
-rw-r--r-- 1 root root 163K Dec 23 15:25 RF.kicad_sym
-rw-r--r-- 1 root root 30K Dec 23 15:25 RF_Mixer.kicad_sym
-rw-r--r-- 1 root root 252K Dec 23 15:25 RF_Module.kicad_sym
-rw-r--r-- 1 root root 8,6K Dec 23 15:25 RF_NFC.kicad_sym
-rw-r--r-- 1 root root 11K Dec 23 15:25 RF_RFID.kicad_sym
-rw-r--r-- 1 root root 162K Dec 23 15:25 RF_Switch.kicad_sym
-rw-r--r-- 1 root root 15K Dec 23 15:25 RF_WiFi.kicad_sym
-rw-r--r-- 1 root root 36K Dec 23 15:25 RF_ZigBee.kicad_sym
-rw-r--r-- 1 root root 6,8K Dec 23 15:25 Security.kicad_sym
-rw-r--r-- 1 root root 8,5K Dec 23 15:25 Sensor_Audio.kicad_sym
-rw-r--r-- 1 root root 364K Dec 23 15:25 Sensor_Current.kicad_sym
-rw-r--r-- 1 root root 3,3K Dec 23 15:25 Sensor_Distance.kicad_sym
-rw-r--r-- 1 root root 13K Dec 23 15:25 Sensor_Gas.kicad_sym
-rw-r--r-- 1 root root 22K Dec 23 15:25 Sensor_Humidity.kicad_sym
-rw-r--r-- 1 root root 48K Dec 23 15:25 Sensor.kicad_sym
-rw-r--r-- 1 root root 97K Dec 23 15:25 Sensor_Magnetic.kicad_sym
-rw-r--r-- 1 root root 97K Dec 23 15:25 Sensor_Motion.kicad_sym
-rw-r--r-- 1 root root 172K Dec 23 15:25 Sensor_Optical.kicad_sym
-rw-r--r-- 1 root root 30K Dec 23 15:25 Sensor_Pressure.kicad_sym
-rw-r--r-- 1 root root 129K Dec 23 15:25 Sensor_Proximity.kicad_sym
-rw-r--r-- 1 root root 254K Dec 23 15:25 Sensor_Temperature.kicad_sym
-rw-r--r-- 1 root root 89K Dec 23 15:25 Sensor_Touch.kicad_sym
-rw-r--r-- 1 root root 4,6K Dec 23 15:25 Sensor_Voltage.kicad_sym
-rw-r--r-- 1 root root 53K Dec 23 15:25 Simulation_SPICE.kicad_sym
-rw-r--r-- 1 root root 229K Dec 23 15:25 Switch.kicad_sym
-rw-r--r-- 1 root root 130K Dec 23 15:25 Timer.kicad_sym
-rw-r--r-- 1 root root 75K Dec 23 15:25 Timer_PLL.kicad_sym
-rw-r--r-- 1 root root 91K Dec 23 15:25 Timer_RTC.kicad_sym
-rw-r--r-- 1 root root 419K Dec 23 15:25 Transformer.kicad_sym
-rw-r--r-- 1 root root 59K Dec 23 15:25 Transistor_Array.kicad_sym
-rw-r--r-- 1 root root 756K Dec 23 15:25 Transistor_BJT.kicad_sym
-rw-r--r-- 1 root root 817K Dec 23 15:25 Transistor_FET.kicad_sym
-rw-r--r-- 1 root root 8,5K Dec 23 15:25 Transistor_IGBT.kicad_sym
-rw-r--r-- 1 root root 52K Dec 23 15:25 Triac_Thyristor.kicad_sym
-rw-r--r-- 1 root root 117K Dec 23 15:25 Valve.kicad_sym
-rw-r--r-- 1 root root 186K Dec 23 15:25 Video.kicad_sym
Do you have these KiCad V6 libraries installed?
An un-install of KiCad does not remove configuration files.
KiCad also does not search for libraries, it only shows libraries listed in the sym-lib-table.
To make KiCad think it started from a clean install, you can simply obfuscate it’s configuration directory by moving (a.k.a renaming) it.
Pasting the next line and executing it in a terminal should do the trick:
mv ~/.local/share/kicad ~/.local/share/2022-01-6_kicad
(Exit KiCad before you execute it, then afterwards start KiCad again).
It also looks very similar to this other post from today:
(Indluding the *.lib files instead of the kicad_sym files)