Hello @DevenBL, what game did you test and what filesystem are you using with the second Steam library folder?
I primarily tested BeamNG.drive and Risk of Rain 2 and the second Steam library folder is using NTFS the os drive is using ext4
Thanks, Proton is known to have finicky behavior with NTFS partitions and this is where your issue came from, not the fact a secondary library folder is in use. We already have several issue tracking NTFS in general in Proton's issue tracker which cover your issue. The general recommendation is to use a Linux native filesystem with Proton.
Closing as a duplicate.
Nothing extracted yet.
Your system information
Please describe your issue in as much detail as possible:
installing games in a secondary steam library on a secondary drive causes games that are run through proton to fail to launch
Steps for reproducing this issue:
at this point the issue has been recreated and the rest was my additional troubleshooting steps: