yep. I took the systemtags app from a backup, ran occ upgrade, occ app:enable systemtags and it is working now again.
Good this will be fixed in 10.0.9. I couldn’t find the systemtags app at all anymore on the market or site from owncloud. Only ended up in the enterprise-only workflow applications when trying to search anything regarding tags.
Anyhow, thanks a lot for pointing this out!