Comment 1 for bug 1834501

I suspect for lxd, this is likely a WontFix; for cosmic and later, it's provided via snap, and unlikely to go back to a deb.

I targeted this against u-r-u as well, as the 'best' fix for this may be to add a check at the start of the upgrade process, and let the upgrader choose at that point what to do, instead of waiting until mid-upgrade to let them know they need to abort the upgrade.

Additionally, whatever warning/error message is printed, either by lxd package->snap upgrade itself, and/or do-release-upgrade, should mention the snap proxy, as enterprise customers with a firewall setup will likely need to use the snap proxy.
https://docs.ubuntu.com/snap-store-proxy/en/