I don't know about Misskey and haven't the opportunity to test it.
I looked for a french speaking instance that doesn't use mastodon because i disliked mastodon's UI. That french speaking instance was using Firefish.
Then Firefish development stopped and the instance moved to iceshrimp. And then, they started rewritting it into #C because it is the dev main language. (Iceshrimp.net)
If i'm not wrong, as one of its dev know jlai.lu that run lemmy, they will add support of Lemmy and PieFed (because i share lot information about PieFed on jlai.lu and its matrix room)
It is for you @AntoineD@kwak.cab :)