Comment 7 for bug 1943840

I opened and closed the stable/ubuntu-21.10 channel for the firefox snap, per https://wiki.ubuntu.com/UbuntuSeededSnaps#Channel_availability.

I then tested a dist-upgrade with my branch of ubuntu-release-upgrader in a clean and fully up-to-date hirsute VM, and I observed that the firefox snap was being installed and the deb uninstalled, and I also saw that:

 - the snap-store snap is being upgraded, as expected

 - firefox-locale-* debs are not being removed, they probably should

 - the gnome-3-34-1804 snap isn't being removed, despite becoming unnecessary (on a clean system with only the minimally seeded snaps − in practice though it is likely that on an actual system there will be other snaps that require it)

 - rebooting after the dist upgrade gives a blank login screen, there appears to be something broken there (probably unrelated to this change)

 - the default firefox launcher in the dock will be removed when the deb is uninstalled, it would be good to replace it with a launcher for the snap