I just flew from DUB to DUS last night. No Einreiseanmeldung form was needed. I checked in online, and the Eurowings check-in form made you check a bunch of boxes confirming that you were vaxed, or have a neg test, or a recovery form etc... Nothing else. Shortly before landing, there was an announcement that airport officials were doing random checks for vax confirmation or tests, etc, but I wasn't checked. I didn't see anyone else get checked. At the passport control, no COVID questions were asked.
Bottom line: You need to conform to the 3G rules, but you might not get asked for documentation.