The nearest decent hills in Germany are probably the Harz mountains (quite a long way east). There will be some online GPS routes somewhere (we only had a couple of days there so haven’t got anything to offer but it did look a very promising area).
The “biggest” hills in Denmark are around Silkeborg. We found some singletrack and talking in a bike shop it sounded like anywhere in the woods was OK.
You need passage of bikes to create singletrack so areas around towns and cities might be most promising. There certainly looked to be good stuff around Gothenburg and SSWC had some fine technical XC trails within riding distance of Stockholm centre.
I think the key is going to be find some local knowledge.