Is there a technical problem on this instance that hides many other communities?
For example if I search all communities for 'games' on this instance it only finds [email protected], but if I do the same search on another instance it finds about 80-100 communities.
I took a look at feddit.ch/instances to see if there are any instances that you block but this is not the case.
Could it be that your instance is somehow configured to only show german speaking languages (that's maybe why it only shows one german community)? I saw another post here about a user unable to comment on certain posts without choosing a language.
The instance doesn’t know about every community on every other instance, boardgames has some subscribers on your instance so it is available. You might try doing a community search for https://lemmy.world/c/games to trigger your instance finding that one. Lemmyverse.net is a good way of finding communities that you could then force your instance to discover.