I went back and fired up Lazarus as my regular user and I got several popups complaining about the installation. So this may be the problem even though I don't see the actual problem. As I said before, this is an Intel i5 (112th Gen) and the OS is currently Ubuntu 21.02. I installed this from the current Debian Packages I found on your web site.
Popup 1:
The current FPC has no config file. It will probably miss some units. Check your installation of fpc.
terry at quickfox:~$ sudo ls -la /etc/fpc.*
-rw-r--r-- 1 root root 7794 Sep 20 13:37 /etc/fpc.cfg
I have looked over the config file and it looks very similar to the config file on my old laptop. The compiler points to /usr/bin/fpc which does exist. Don't know where fpc defines it's source directories.
terry at quickfox:~$ ls -la /usr/bin/fpc
-rwxr-xr-x 1 root root 508112 Jul 6 2020 /usr/bin/fpc
Popup 2:
The project uses target OS=linux and CPU=x86_64. The system.ppu for this target was not found in the FPC binary
directoies. Make sure fpc is installed correctly for this target and the fpc.cfg contains the right directories.
ls -la /usr/lib/fpc/3.2.0/units/x86_64-linux/rtl/system.ppu -rw-r--r-- 1 root root 882770 Jul 6 2020
/usr/lib/fpc/3.2.0/units/x86_64-linux/rtl/system.ppu
I don't know where the rtl is defined in Lazarus, but the file is there. Also, I have compiled a few toy pascal programs and they seem to compile and run fine. Lazarus seems to compile them too after complaining.