I'm not sure if the other one is official meaning Mihoyo endorses it but I made this community since there was no community for genshin when I joined lemmy. Decided to make a place for people to discuss genshin and since it was the only one for a while more people joined this one. It would be possible to merge them but it seems like the post are the same on both

This one seems to have actual user activity, the other one has zero comments.

(And since when do we care if a community is "official"? If we did, we would be on the HoYo forums 🤷‍♂️)