They actually do have an English only policy for public posts; if you use a content warning on your post you can speak in any language you like.

I'm still a bit baffled that they do it like that, but it is what it is ¯⁠\⁠_⁠(⁠ツ⁠)⁠_⁠/⁠¯

And if I'm moving out of Fosstodon, I'll probably move to Nostr anyway ✌️😎