OMG, that was it. I would have never figured that out in a million years. Within WMR portal, under settings, there is “set up OpenVR” that resets this setting within SteamVR (go figure!). Everything is back to normal now. How it is possible that there are SteamVR options that cannot be undone unless you use another software (without any warning to the user), and how it can be that choosing SteamVR as your runtime can reduce MFS fps to 1 (no kidding) are prolly questions for another day…