I’ve found out the solution to this, the hard way. Stuck me for months when I first came across to Linux earlier this year, so here’s the solution so you don’t have to suffer my pain:
Put the game libraries on an ext4 drive. Steam in Linux doesn’t like to run games, particularly those requiring Proton, from an NTFS partition. Even with the proper ntfs-3g driver installed and running (I could browse and write to the drive fine otherwise) it would NOT run games from it unless they were native, and even then not all the time.
For me, when I hit play it said “Running”, then a few seconds later it would just return to saying nothing, as if I hadn’t hit play at all.
Only when I made the effort to shift 1Tb of games from my NTFS hdd to my ext4 hdd did I see a difference, and it was an immediate difference at that. Games that refused to run, ran perfectly, as if they were native games.
Made a huge difference, so give that a go, because NTFS partitions, while usable in Linux, can act funny, especially if you’re dual-booting between Win & Linux (Windows 10 for example doesn’t shut down properly and can lock NTFS partitions making them unusable at all in Linux - another thing I learnt the hard way).