It’s in the direct “download” section. Choose your closest linux distro there: https://kicad.org/download/
I used the Mint variant: https://kicad.org/download/linux-mint/
Near the bottom of the page you find:
sudo add-apt-repository --yes ppa:kicad/kicad-dev-nightly
sudo apt update
sudo apt install kicad-nightly
PPA’s are a “Ubuntu” thing, the do not work on all Debian based distro’s. If it’s straight Debian, you probably have to use a backport. If you can install the binaries this way, then it should also install the libraries and configuration for preferences etc. This is the path of least resistance.
I guess you meant “apt” here?
I’m not sure what KiCad V5.99 does if you install it from source. One of the possibilities is that the Symbol and Footprint libraries do not get installed at all. KiCad V5.1.8 and V5.99 can both be installed at the same time. I installed via the above repository, and “-nightly” is added to all sub programs, so this works:
paul@medion:~$ eeschema-nightly
In the same manner I’ve also got the libraries installed twice:
paul@medion:/usr/share$ ls -hld kicad*
drwxr-xr-x 8 root root 4,0K Oct 21 14:21 kicad
drwxr-xr-x 6 root root 4,0K Dec 4 16:24 kicad-nightly
Euhm, except that the libraries themselves are links to other locations:
paul@medion:/usr/share/kicad-nightly$ ls -hl
total 20K
drwxr-xr-x 17 root root 4,0K Nov 17 11:03 demos
-rw-r--r-- 1 root root 193 Dec 4 11:20 kicad-nightly.env
lrwxrwxrwx 1 root root 43 Jul 7 11:47 library -> ../../lib/kicad-nightly/share/kicad/library
lrwxrwxrwx 1 root root 43 Jul 7 11:47 modules -> ../../lib/kicad-nightly/share/kicad/modules
drwxr-xr-x 2 root root 4,0K Dec 4 16:24 plugins
drwxr-xr-x 4 root root 4,0K Nov 17 11:03 scripting
drwxr-xr-x 2 root root 4,0K Dec 4 16:24 template
On (most?) linux distro’s you can also just install the libraries as separate packages. If you do this, you may have to fix the paths to the libraries manually.
First use “apt search” to see what kicad packages are available, and then use “sudo apt install” to install the packages you want.
paul@medion:/usr/share/kicad-nightly$ apt search kicad
i kicad - Electronic schematic and PCB design software
p kicad-common - Old common files used by kicad - Transitional Package
p kicad-dbg - Debug symbols for kicad
i kicad-demos - Common files used by kicad
p kicad-doc-ca - Kicad help files (Catalan)
p kicad-doc-de - Kicad help files (German)
i kicad-doc-en - Kicad help files (English)
p kicad-doc-es - Kicad help files (Spanish)
p kicad-doc-fr - Kicad help files (French)
p kicad-doc-id - Kicad help files (Indonesian)
p kicad-doc-it - Kicad help files (Italian)
p kicad-doc-ja - Kicad help files (Japanese)
p kicad-doc-pl - Kicad help files (Polish)
p kicad-doc-ru - Kicad help files (Russian)
p kicad-doc-zh - Kicad help files (Chinese)
i A kicad-footprints - Kicad footprints (modules)
i A kicad-libraries - meta-package for dep to all KiCad libraries (symbols, fo
p kicad-locale-bg - Bulgarian locale for KiCad
p kicad-locale-ca - Catalan locale for KiCad
p kicad-locale-cs - Czech locale for KiCad
p kicad-locale-de - German locale for KiCad
p kicad-locale-el - Greek locale for KiCad
p kicad-locale-es - Spanish locale for KiCad
p kicad-locale-fi - Finnish locale for KiCad
p kicad-locale-fr - French locale for KiCad
p kicad-locale-hu - Hungarian locale for KiCad
p kicad-locale-it - Italian locale for KiCad
p kicad-locale-ja - Japanese locale for KiCad
p kicad-locale-ko - Korean locale for KiCad
p kicad-locale-lt - Lithuanian locale for KiCad
p kicad-locale-nl - Netherlands locale for KiCad
p kicad-locale-pl - Polish locale for KiCad
p kicad-locale-pt - Portuguese locale for KiCad
p kicad-locale-ru - Russian locale for KiCad
p kicad-locale-sk - Slovak locale for KiCad
p kicad-locale-sl - Slovenina locale for KiCad
p kicad-locale-sv - Swedish locale for KiCad
p kicad-locale-zh - Chinese locale for KiCad
i kicad-nightly - Electronic schematic and PCB design software
p kicad-nightly-dbg - Debug symbols for kicad
i A kicad-nightly-demos - Common files used by kicad
i kicad-nightly-footprints - Kicad footprints (modules)
i kicad-nightly-libraries - meta-package for dep to all KiCad libraries (symbols, fo
i kicad-nightly-packages3d - Kicad packages3d (3d models for footprints)
i kicad-nightly-symbols - Kicad symbols (schematic)
i kicad-nightly-templates - Kicad templates
i A kicad-packages3d - Kicad packages3d (3d models for footprints)
i A kicad-symbols - Kicad symbols (schematic)
i A kicad-templates - Kicad templates
p libglm-kicad-dev - C++ library for OpenGL GLSL type-based mathematics
p libglm-kicad-doc - documentation for the OpenGL Mathematics (GLM) library