Thank you or the detailed report!
I’m going to do a new pass on this script soon and try to improve the parts that gave you some difficulties.
For realpath I’ll simply add it to the dependencies check so the script will fail with an explicit error if the command isn’t available, instead of going on anyway and failing without explication later.
For df I’ll see if I can find a more backeward compatible way do do this test (you got what it should do, checking free space in /tmp to see if the package can be built there).
About the mpv dependency I’m actually suprised I left the 'any' dependency that will cause problems for some people. I should be able to use a more compatible way to do this check quite easily.
Lastly about multiplayer, I didn’t test it yet but will do it. If in the meantime you can find some way to get it working please share it here ;)