I noticed some time ago the feed stopped working. I used to follow it
using the gwene.org gateway, but even following the link from
https://www.archlinux.org/feeds/ to
https://wiki.archlinux.org/index.php?title=Special:RecentChanges&feed=rss
sends me to a "Login Required" page.
So apparently either the feed is gone for good intentionally (I hope
not) and shouldn't be listed, or is broken and should be fixed?
I think you are bitten by changes introduced in the wiki update ~10
weeks ago. See [0] for details.
[0]
https://lists.archlinux.org/pipermail/arch-dev-public/2019-September/029664.html