OK, after scratching my head a bit further I got it.
Noticed some ERROR logs during startup complaining about DB corruption even on the old version. I am guessing that if there are such logs at startup then Plex doesn’t apply any database migrations required to support new features.
So I suppose the new DB table needed for the home screen not being created broke it and other recommended screens.
Anyway, followed https://support.plex.tv/articles/201100678-repair-a-corrupt-database/, repaired my DB and then retried the upgrade; now my server seems fine.
Would really be great if Plex had a way of warning you of a corrupt DB by a notification/something at startup so you could fix it as soon as possible (or rollback to a backup) :-/ In this case it must have broadly kept working for some indeterminate period of time until this server update needed a new table, meaning now I’m not sure even when the corruption was introduced or what data I have lost. :-/
Suggest you look at your logs for the same thing @dimensionzero and see if you need to repair?
