Problem with feed of trisquel-users section in liferea

For a couple of days now I get an error from liferea using the link https://trisquel.info/en/forum/trisquel-users/feed. The message is:
---
There were errors while parsing this feed!
Details
Could not detect the type of this feed! Please check if the source really points to a resource provided in one of the supported syndication formats!

XML Parser Output:
The URL you want Liferea to subscribe to points to a webpage and the auto discovery found no feeds on this page. Maybe this webpage just does not support feed auto discovery.Could not determine the feed type.

You may want to contact the author/webmaster of the feed about this!
---

I am writing this post, because I couldn't find a way to contact the webmaster of this forum.