Hmm, strange. That said: We will need to see a glimpse at that "details for nerds" bit in your screenshot to potentially troubleshoot the issue, and we need to know your OS as well.
Thanks for the extra info! That wasn't quite what we needed but from here onward, it may be more useful for you to send us an email @ contact@moiraimyths.com (or, if you would prefer DMs, you can send me a friend request on Discord via @fatefulclotho) since this thread is getting long and we don't want to ask for a screenshot of your system settings on a public comment section.
For anyone reading this and having a similar issue: If/when we find a solution, we will update this thread and put out a devlog with instructions on how to fix it.
146 days ago(+1)
Update for others reading this thread: We're unsure what the original issue was, but Steam seems to work now :)