This comes from Linux Mint 21.1, which is based on Ubuntu 22.04.

mint@mint:~/GOG Games/Sanitarium$ ./start.sh
Running Sanitarium
./scummvm/scummvm: error while loading shared libraries: libSDL2_net-2.0.so.0: cannot open shared object file: No such file or directory

I did this and the issue went away: apt install libsdl2-net-2.0-0

Then I ran into this error:

Running Sanitarium
./scummvm/scummvm: error while loading shared libraries: libfluidsynth.so.2: cannot open shared object file: No such file or directory

As there is no libfluidsynth version 1 in the repository, I tried installing libfluidsynth3 and I was told it was already installed. But the same complaint comes up when trying to run Sanitarium, so this is where I got stuck.

Check if creating a symbolic link to your libfluidsynth libtrary would work.

Something like:
cd /usr/lib
sudo ln -s libfluidsynth.so.3 libfluidsynth.so.2

That's an example command. Your location of libfluidsynth or extension may be different -- you could do a "find" first to see the xorrect details for it.

Solution was suggested here for a similar issue (with Blade Runner on Manjaro linux):
https://www.gog.com/forum/blade_runner/get_it_running_on_manjaro_linux

Thanks, that worked. :)

mint@mint:/$ cd /usr/lib/i386-linux-gnu/
mint@mint:/usr/lib/i386-linux-gnu$ sudo ln -s libfluidsynth.so.3 libfluidsynth.so.2
mint@mint:/usr/lib/i386-linux-gnu$ cd ../x86_64-linux-gnu/
mint@mint:/usr/lib/x86_64-linux-gnu$ sudo ln -s libfluidsynth.so.3 libfluidsynth.so.2

The game only started after I made the symbolic link in the x86_64 directory, but having both seems like a better idea. :)

P.S. I hope the GOG package will be updated. It would be nice for it to just work - the Windows release worked fine for me with Wine, when I played it.

Thank you! It also worked for me.
C: