Hello there, I have the same problem with fpcupdeluxe. I also have LAMW_manager installed, which installed fpc from the repository.
It worked before, but after I deleted the fpcupdeluxe install folder(after installing lamw_manager, i think)
it won't recompile now, even if I completely delete everything in the fpcupdeluxe folder.
Linux Mint 19.3 Cinnamon
Lazarus 2.0.6
FPC: 3.0.4
x86_64