This is a significant regression. In previous releases, users could update which software sources they wanted to use via software-properties-kde. I did discover this is in Muon discover now, but that's a non-discoverable change (I only found it while researching to file this report). Personally, I regularly use the updater and virtually never used Muon software center and have never used Muon discover. Moving useful functionality from an application I use regularly to one that I don't is not helpful. Reproducible: Always
You should have it in "More...>Advanced...>Configure Software Sources". There's been changes there, to verify see the 2.1 branch.
Created attachment 83294 [details] screen shot In 2.1.0, for me, the advanced section is disabled. Is this changed in 2.1.1?
Confirmed fixed for 2.1.1.