If you're willing to drive to a site >150 km away, the Burgwald north of Marburg in Hessen is locally famous for its population of Tengmalm's and Pygmy Owl. They offer guided tours too, though I'm not sure when.
Otherwise, I don't know exact owl data about the region. Including the two aformentioned ones, there's seven species of them that are widespread throughout the country, but all are challenging to see (Tawny Owl and LEO should be the easiest). Eagle Owl has become surprisingly common again, at least in some regions.
Ural Owl has been reintroduced in the Bavarian Forest (which is on the other side of the country) and there are rumours of a population of Scops Owl in the Southwest or nearby, though maybe that's just some vagrants. SEO are mainly confined to coastal regions in the NW, so these three species are probably not very relevant to you.
Regarding non-owls in the region, there's the vineyards at Rüdesheim that should yield Rock Bunting and Cirl Bunting, with a bit of luck. that place is "just" about 100 km away, might be accessible via public transport (but I've never been there, so can't confirm).
The Wahner Heide near Cologne should be interesting too, although some of the species typical for this habitat (Nightjar, Hobby, Red-backed Shrike) will have already left for Africa.
Some other local species like Black Stork and Black Kite might have already left at this time of year, too.
