Purging a snap that has a single active revision is needlessly complicated:
# snap list --all | grep cups
cups 2.4.12-2 1100 latest/stable openprinting✓ -
# snap remove --purge --revision 1100 cups
error: cannot remove "cups": cannot remove active revision 1100 of snap "cups"
# snap remove --purge cups
2025-06-04T13:24:21Z INFO Waiting for "snap.cups.cups-browsed.service" to stop.
cups removed