Hm, for me it is not working with the links above. I can subscribe to communities, then their posts show up in my feed and I can interact with them. I can also search a community or few the list of subscribed communities. Then it works like intended. The link I follow then looks like this: https://feddit.de/c/memes@lemmy.ml

But I think this is not a universal link that will work for all instances, but only for users of Feddit.de.