Thanks for response, I'm using the board feeds
After checking the configurations:
- https://forum.libreelec.tv/board-feed/ result in error 404
- Tiny Tiny RSS is configured with individual feeds like https://forum.libreelec.tv/board-feed/14/. They do exist, the validator agree with them but IMO choke on them.
Solution:
The forum software is now using https://forum.libreelec.tv/thread-list-rss-feed/ as root URL. After changing the reader configurations it seem to be working again.
Will close the thread after a few successful dates.