We just released an update which changes how we handle SSO, a full description of the changes will be posted in c/changelogs once the update is stable.
Please use this thread to notify of any issues with things like being logged out, being redirected to the old domain, etc. If you have a bug report, please also include what browser (ex. "Chrome") and version (ex. "89.0.4389.90") you're using, and whether you're using any privacy blocking extensions.
If you do get "logged out", it may not be as it appears. There's two options: for some browsers, you can wait a few seconds and you'll be automatically logged back in. If you aren't, then you can click the sign in button, and you may be immediately logged back in without having to re-enter any details. This would be the intended behavior for some privacy focused browsers and extensions, as well as some old browsers.
Got logged out of Safari 12.1.2 and clicking the "Sign in" loads authentication which then immediately reloads the main page, but without logging in. Running uBlock Origin 1.16.0.
Works fine on Brave.
Are you able to test whether Safari 12.1.2 works correctly without uBlock Origin?