Thank you for your fast reply.
Unfortunately there is no bUpdater Key in my ~/Library/Preferences/com.adobe.Acrobat.Pro.plist.
For good measure, I completely trashed the old plist, but the issue remains the same. If I filter the plist file for "upd", I´m just getting the following results:
Could it be, that bUpdater Key is just for the Continuous update track of the subscription versions and not for the Classic update track that serves my perpetual TLP version?