We are aware of all the printing-related problems in Mantic, as we tried a switchover to the using the CUPS Snap instead of the usual Debian packages to provide the printing stack. Unfortunately, we did not succeed to complete all the needed desktop integration in time and therefore we have withdrawn from this switchover. It is possible that we have overlooked some packages when returning to the original state. This we will naturally fix before the release.
See also: CUPS Snap - Call for testing
Sorry for the inconvenience.