I am a little puzzled by the new version fp-3.0.4 !
I use computer science since 1966 and I can't do anything with the Fpc comiler under IDE : It says impossible to find unit "system" . Is it possible for a brand new mounting under Ubuntu 18.04. Nothing works also under Buster/Rpi4 4Go !
To work I have mended an old fp-3.0.0 (not again in the distribution !) from another computer (Core-i7 instead of Bi-Xeon Quad)
and now everything work well with the system Ubuntu.
. But I need to do calculations on "black holes" the beautiful graphics units PtcGrah and PtcCrt (more than 400 time faster than Graph and Crt !). So, to work elsewhere than Windows, I use first,
the old version fp-3.0.0 with PtcGrah+PtcCrt and for the Raspberry world I use the Wheezy/ RPi3 to compile the interoperable PASCAL source to execute it after under Buster/ Rpi4 that have not the necessary units.
It is confusing for me to ask about systems, I know nothing to it, but to do scientific calculations (like monte-carlo ones) FPC-Pascal with PtcGraph is necessary to do experimental calculations ... I pray you to have operational package . Friendly. Yves.