If I understood the issue correctly (and I may very well be mistaken!) the problem Mint has with Canonical is that Ubuntu has "hijacked" (for lack of a better term) some apt packages so that they now actually install snapd and the snap. So you think you're opting out of snap, but when you use apt to install Chromium you end up using snap anyway.
If I understand correctly, this is Mint's main complaint: that Ubuntu seems to be hijacking apt packages with snap.