Since the eye tracking update from April 13 (manifest ID 6690722139491075971), VRChat deadlocks with a memory leak when started in VR mode (desktop mode is unaffected). This happens when running it on Linux through Proton (any version, 7, 8 and experimental).
This has been confirmed by several people, as can be seen on the Proton issue tracker:
Right after the eye tracking update this was only a minor issue, as killing the VRChat process and restarting it a few times usually made it work after 3-5 attempts. The most recent updates (on May 2 and 3) made it progressively worse, to the point where sometimes one could get lucky after 30 retries, but sometimes even 60 are not enough. Each try takes 50-60 seconds, so trying to get in with 30 attempts already takes up half an hour.
I can confirm that it still works with the build released before April 13, which is manifest ID 738841166574277673 from March 22.
Some people suggested that this might be due to dependency changes related to VR, but according to MehStrongBadMeh he is not aware of and such dependency updates since the eye tracking update.