THAT'S why my Steam library was acting up? I had migrated it to the new SSD that I installed Fedora onto, because I thought the ancient HDD was starting to finally give out, and doing this fixed it. But it was because I was still using the NTFS partitions from when I was using Windows??? What the hell
It's because whatever disk partition your steam library folder is in needs to support at least two things:
- UNIX-compatible symlinks
- Colons in the filename
It also greatly prefers to have UNIX style ownership and permissions and Extended Attributes, but I'm not certain these are 100% mandatory.
Vanilla wine technically only needs these on your home directory since it defaults to everything sharing one "prefix" (combination configuration directory / virtual windows installation), but Steam's Proton makes a separate prefix for every game, in $STEAMLIBRARY/compatdata. So if your library is on a not-strictly-unix flavored filesystem like SMBFS-from-a-unix-server, NTFS, or older versions of ExFAT, it might be possible with the right driver and mount options to get it mostly-working, but it's delicate.
The worst part is, I'm not sure why this is still the case. AFAICT, Wine/Proton only really need symlinks for drive mapping. A DOS-style C:\Folder\file path gets rewritten as $PREFIX/dosdevices/c:/Folder/file. with the colon in the filename. Valve could seriously improve compatibility by changing the rules a little so that the dosdevices symlinks don't need the colon, and could basically fix everything by storing the drive mappings in an ini file.
