I have two PCs. The last thing I recall doing on Steam on either one of them was opting in to the 0.17.2 beta. I got busy with work and didn't get to try to play anything for a couple of days.
Now Steam will not successfully load on either one. It runs the Steam auto-updater, it logs me in, and then it immediately vanishes. I don't typically get to see the main Steam window at all, although I have somehow gotten it once or twice by manually clicking on game executables directly - but it only stays up for a second or so before crashing.
I have rebooted, I have run Windows update, I have updated my Internet filter, I have tried disconnecting from the internet to log in offline, I have ensured that no other programs are running, I've reinstalled Steam, and I've tried everything else I could find on Google.
So - how do I, from outside of Steam, tell it to roll back to 0.17? This was the last thing that got changed before Steam started failing, so I believe at this point that it's a likely candidate somehow.
One thing that I find odd is that when I go to Steam\Steamapps\common\ , the Factorio files appear to generally have not been modified since 2018 (\common\Factorio\bin\x64\factorio.exe has not been modified since 6/18/2018).
Here are some crash logs, selected from my last few attempts to run Steam.
appinfo_log
bootstrap_log
configstore_log
appinfo_log