Hi,

If I try to include http://www.forum.joomgallery.net/index.php?type=rss;action=.xml as source, I am able to save it as rss feed but when I want to update the feed I always get an Error 403 Forbidden.

This source works for me just fine.

Another problem is the rss feed from xda-developers.com.
I am not able to include the feed in selfoss. Is there a way to add a forum or thread from xda-developers as rss feed?

I found the following feed:

https://forum.xda-developers.com/external.php?type=RSS2

but it prints

Must be logged in to get external feeds.

and after I log in, it just shows

Forbidden

Not much we can do about it, you should write the forum support.