Great news, for a great and defining software of the Ubuntu MATE distribution, @lah7.
If the Welcome Screen is the king, the Software Boutique is the crown that sits on its head.
Hopefully with some support for changing sources.
Meh! It's been my experience that user comments and reviews are, generally speaking, the poorest and least credible source of information. But it is also my experience that people usually call me a cynical old b.astard. Right!