OK, time for a second attempt at major intervention with the matsodon.acc.sunet.se instance, starting in 1-2 hours from now, and downtime hopefully not lasting more than 1-2 hours either.
Well, that took longer than I hoped, but mastodon.acc.umu.se is done now. I think it is a bit too late to start with mastodon.acc.sunet.se now, so maybe tomorrow?