I just wanted to update my system (where is the Update Manager in MATE btw? I had to start it from the terminal because I couldn't find it) but because I have included the Steam repository the manager told me there were untrusted sources included, and cancelled ALL updates!
First, if I included Steam then I trust it, but what I'd really like to see is ALL THE OTHER UPDATES APPLIED!
Fine, you don't trust a source (even if I do), but for crying out loud why on earth stop updates from all the other sources?
Makes absolutely no sense to me.