I know I have to compile it with make/cmake, but LibreElec doesnt have the apt package manager so I installing stuff is very hard, I don't have gcc, nor make, nor cmake, i dont even have git. Is there an alternative option? Is it possible that I compile it on my pc and then transfer it to the LibreElec? Do you have any other suggestions?
Install from dEXE's Kodi Repository, there you have versions 20.7.6 for LE11 (armv7a) and 21.7.6 for LE12 (aarch64) for RPi 4 or 5... and 21.7.8 versions for Android too...