Are you the first subscriber from you instance? If not, I see feddit.org supports Lemmy Federate. You could try adding the new communities there first?

I cannot subscribe

details needed

I wouldnt be surprised if they defederated db0. For whatever reason the german instances are very hostile to anything mildly controversial, no porn no piracy and so forth. Basically the main reason I haven't made an account there despite der Tatsache dass ich auch Deutscher bin.