I am using KiCad 8.0.7 on GNU/Linux (Zorin OS) with an AMD 9800X3D (no graphics card) and I encounter lag spikes, i.e. it is not overall slow or laggy, but often times I get short freezes, even in the schematics editor.
Has anyone had a similar problem?
I don’t recognize your problems, but updating video card drivers often helps for fixing problems with them.
Unfortunately Zorin is an unsupported Linux distribution.
What happens if you switch between accelerated and fallback graphics rendering?
What do you mean by unsupportted? Zorin OS is based on Ubuntu.
Only platforms (distros) mentioned explicitly are officially supported. It doesn’t mean the others don’t get help or that bugs won’t be fixed on other platforms. It means that the development team whose members can debug and fix bugs use only certain platforms and haven’t promised to debug problems on other platforms.
The bugs which don’t appear on all platforms often depend on subtle differences which may vary even between the variations of the same distro. For example the desktop environment on Linux is a typical part of the distro which can vary between differently named distros even they are based on the same distro or are variations of a supported distro.
It may be based on but it’s not Ubuntu . . . if it were why wouldn’t you just use Ubuntu.
Zorin OS17 is based on Ubuntu 22.04. What changes were made to stop being Ubuntu is unspecified
If your Zorin is using Wayland that might be the issue:
Regardless of the window manager, KiCad officially only supports the X11 backend. Users who choose to use Wayland will have to run KiCad in the compatibility layer XWayland.
I use X11 
Probably it has something to do with the AMD drivers, I recently had a total freeze in KiCad, but it may also come from a total different appliation (e.g. Chrome or a Chromium based application):
Linux office-linux 6.8.0-49-generic #49~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Nov 6 17:42:15 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: [gfxhub] page fault (src_id:0 ring:24 vmid:4 pasid:32770, for process chrome pid 32279 thread chrome:cs0 pid 32393)
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: in page starting at address 0x000000003f800000 from client 0x1b (UTCL2)
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: GCVM_L2_PROTECTION_FAULT_STATUS:0x00401430
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: Faulty UTCL2 client ID: SQC (data) (0xa)
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: MORE_FAULTS: 0x0
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: WALKER_ERROR: 0x0
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: PERMISSION_FAULTS: 0x3
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: MAPPING_ERROR: 0x0
Dez 09 12:53:28 office-linux kernel: amdgpu 0000:69:00.0: amdgpu: RW: 0x0