In that case, it seems to be a good idea to setup a linux installation yourself for the user and not give them sudo (or root password) and then make a service allowing them to use the app store and updating their system without requiring root privileges, but not letting them add a repository.
Gaming on Linux can still be considered difficult in general. The main reason I don’t have any difficulty is because the few games I play are well supported on Linux, giving me few to no crashes. Playing Elite Dangerous (Epic version) on wine seems to be causing memory leaks over time, making me have to restart every 5 hours, but Linux supported games I get from GoG work perfectly for normal scenarios normal => Single monitor 60FPS.
Apart from gaming, Linux has been a charm. But I am one of those ppl who likes programming and creating my own solutions for problems (which fits well with Linux), so I can’t say the same to someone who just wants “a solution. Any solution”.