Anecdotal, but I had similar symptoms (monitor loses signal for some seconds before audio stops) on a dying Nvidia 1050 Ti a couple of years back. It wasn't Proton-specific though.
Example of my journal logs from that time:
kernel: NVRM: GPU at PCI:0000:01:00: GPU-4e72f118-b055-bc4b-f1a4-e7d67fed003e
kernel: NVRM: Xid (PCI:0000:01:00): 79, pid='<unknown>', name=<unknown>, GPU has fallen off the bus.
kernel: NVRM: GPU 0000:01:00.0: GPU has fallen off the bus.
kernel: nvidia-modeset: ERROR: GPU:0: Failed to query display engine channel state: 0x0000927c:0:0:0x0000000f
Reference for XID error codes: https://docs.nvidia.com/deploy/xid-errors/analyzing-xid-catalog.html
I appreciate the corroboration, but my gpu exhibited no issues prior to switching to Linux, and my crashes (rather annoyingly) leave no trace within journalctl.
proton experimentalx1 2025-12
In rather demanding games and only games , such as Astroneer, Helldivers 2, Ready or Not, and more, my system will soft-crash. I say soft-crash, because the fans keep spinning and audio continues for a few seconds longer, but both monitors stop receiving a signal - the only way to recover from this state is to restart the PC.
I've tried submitting a bug report on the Nvidia forums, but they've been less than helpful. In truth I'm not 100% sure it's a proton issue, but the only games that crash like this are running via proton.
Attached below are the proton logs for Astroneer running with proton experimental:
steam-361420.log