I tested the latest version of the release-upgrader in -proposed for Bionic and the gtk-common-themes snap is tracking latest/stable/ubuntu-18.04.
bdmurray@clean-xenial-amd64:~$ snap list Name Version Rev Tracking Publisher Notes core18 20210309 1997 latest/stable canonical✓ base gnome-3-34-1804 0+git.3556cb3 66 latest/stable/… canonical✓ - gnome-calculator 3.38.2+git3.1d166209 884 latest/stable/… canonical✓ - gnome-characters v3.34.0+git30.16311a5 708 latest/stable/… canonical✓ - gnome-logs 3.36.0 103 latest/stable/… canonical✓ - gnome-system-monitor 3.38.0-17-g38c1ce1d62 157 latest/stable/… canonical✓ - gtk-common-themes 0.1-50-gf7627e4 1514 latest/stable/… canonical✓ - snapd 2.49.2 11588 latest/stable canonical✓ snapd bdmurray@clean-xenial-amd64:~$ snap info gtk-common-themes name: gtk-common-themes summary: All the (common) themes publisher: Canonical✓ store-url: https://snapcraft.io/gtk-common-themes contact: https://gitlab.gnome.org/Community/Ubuntu/gtk-common-themes/issues license: unset description: | A snap that exports the GTK and icon themes used on various Linux distros. snap-id: jZLfBRzf1cYlYysIjD2bwSzNtngY0qit tracking: latest/stable/ubuntu-18.04 refresh-date: today at 10:56 PDT channels: latest/stable: 0.1-50-gf7627e4 2020-11-27 (1514) 67MB - latest/candidate: 0.1-52-gb92ac40 2021-04-21 (1515) 68MB - latest/beta: 0.1-52-gb92ac40 2021-04-21 (1515) 68MB - latest/edge: 0.1 2020-04-17 (1503) 58MB - installed: 0.1-50-gf7627e4 (1514) 67MB - bdmurray@clean-xenial-amd64:~$ snap info gnome-3-34-1804 name: gnome-3-34-1804 summary: Shared GNOME 3.34 Ubuntu stack publisher: Canonical✓ store-url: https://snapcraft.io/gnome-3-34-1804 license: unset description: | This snap includes a GNOME 3.34 stack (the base libraries and desktop integration components) and shares it through the content interface. snap-id: TIM9dBBJEceEjMpwaB3fiuZ3AdSykgDO tracking: latest/stable/ubuntu-18.04 ... bdmurray@clean-xenial-amd64:~$ grep "release-upgrader version" /var/log/dist-upgrade/main.log 2021-04-21 10:02:47,348 INFO release-upgrader version '18.04.44' started -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1922297 Title: 20.10 to 21.04: snap does not upgrade channel To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1922297/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs