[System] Transition from 'SteamVRSystemState_Ready' to 'SteamVRSystemState_NotReady'.
[Status Alert] SteamVR Fail (-301)
[System] Transition from 'SteamVRSystemState_NotReady' to 'SteamVRSystemState_Ready'.

Now that I think about it I have x570 motherboard and they're known to have issues with USB connection.
This might be connected to that, I will try to update BIOS if possible and tinker with other USB related settings to see if it helps.
EDIT: I don't have any problems with any other USB device.

It is not very likely an USB issue because playing Walking Dead Saints and Sinners this doesn't happen.
So far that is only game I have found where this doesn't happen.

I did clean install of Ubuntu 20.10 on different disk and installed everything needed to play SteamVR still the same problem. Seems to be hardware related then...

The culprit is haptics. When I disable haptics no more errors or state changes in the vrmonitor log.
I would really like to get this fixed since haptics are essential in VR in my opinion.

Thanks for this info.
I'm using the VR mirror window to capture VR footage, and it had blackouts again and again (the window goes black for a second, then the 1st person view of the VR game shows up again), where I could shortly see a "Steam VR failed 301" error window, but I don't notice anything in the VR headset itself.

I disabled haptics for the index controllers for that game (After the Fall 751630) via web browser (http://localhost:27062/dashboard/controllerbinding.html) as the in VR dashboard controller settings take forever to load, and the issues was mitigated almost completely.

There was only one more blackout observed during a 2 hour session, while otherwise there had been blackouts depending on load, framerate etc several times a minute.

I also had the impression frame times became much better/smoother when haptics had been disabled.