I did find some existing communities with https://browse.feddit.de/
But they seem very empty.
A community all about learning languages!
Other Lemmy language communities:
Other communities outside Lemmy:
I would be interested in this, but unrortunately don't have the time to run it myself.
The communities exist. The user base doesn't. I guess we just gotta pick one, join/subscribe/post/comment, and hope that eventually there will be some traction.