URLs with /c/ are treated as community links.

Not sure how you'd go about fixing this. But in the comment https://sopuli.xyz/comment/19414295 is a link to https://www.youtube.com/c/Partiz%C3%A1nm%C3%A9dia/streams that Summit tries to open as a community. Maybe you can continue on to the normal Android link handling if no Lemmy or Piefed API can be found on the server.