Looks like this is a duplicate of
https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1639863.
If I'm not imagining that Firefox and Thunderbird showed up in Discover
recently, then that means that Ubuntu users have been unable to use
GNOME Software or KDE Discover to install the FOSS world's
For Firefox, this looks like it's the fault of Firefox (or rather the
firefox package) itself (I guess someone symlinked an icon again), see
http://appstream.ubuntu.com/artful/main/issues/firefox.html
Krita on the other hand should show up, and I can see it. Can you check for
that again? Maybe
