Mastodon 3.3.0 breaks SSO (and more?)
After upgrading to 3.3.0 things escalated a bit. First SSO login broke. That resulted in a roll-back. But not very successful, because it broke notifications for the old version.
moving to the newer version again, with a now valid session got me around the SSO problem but notifications still didn't work. Now old notifications were showing up, but new notifications no longer arrived.
With a restore of a backup from today, it was possible to get the instance up and running. Using version 3.2.2.
Further investigation is needed.