No game should require root permission on Linux. I can't run it since it requires it to proceed and fails if I cancel.
I use firejail for security - it's a sandbox program as I mentioned - and new programs are run inside firejail by default. I can't see what program it's trying to run when the installer says firejail there so I don't know what changes to make to firejail to try to get it working. I don't have trouble with other games in Itch. So far this is the only game I've had this issue with.
If you could suggest which programs it might be trying to run/install I could try to whitelist or install them and see if the problem goes away.
I honestly have no idea why you're seeing that message, Tanath. This did not pop up in all the tests the QA company did when testing Hidden Folks on Linux. I can't find anything regarding Unity & Firejail on google, don't know what Firejail is, and I don't have a Linux computer or any knowledge of Linux to be of any help. If you can figure out what Unity wants from Firejail, I think that's your best bet in solving this issue.