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.
The search feature doesn't seem to be working
Re-enabling once this update is stable
Search has now been re-enabled. Note that it may be disabled again if this SSO update is reverted (which may occur if the update completely breaks the site for a browser with a significant market share)