There was a minor issue with the GitHub OAuth logins, but that appears to be resolved now. As always, let me know if you see any further issues. I will wait until next week before looking at the new plugins we want, to allow a chance to spot issues.
It looks like some people are seeing broken UI issues when returning to Redmine - apparently clearing cookies is helping for some, for others it’s a force-reload of the page (Ctrl-Shift-R in Firefox, I think). Looks like some state is stored client-side that is invalid for the new version of Redmine…