How can mbin/kbin users subscribe or even just reach a lemmy community?

I’m trying to access this community from fedia.io:

https://sopuli.xyz/c/french

Searching for that URL or !french@sopuli.xyz yields nothing. If I manually visit this URL:

https://fedia.io/m/french@sopuli.xyz

I get a 404.

btw, this post would be better suited in

https://fedia.io/m/Mdev@kbin.run

but when I try to post there I get:

This page isn’t workingfedia.io is currently unable to handle this request.
HTTP ERROR 500

Which makes this post herein relevant to the fedia magazine after all.