Bazaar, Upstart, Mir, Snap. Canonical really likes to do their own thing and usually it fails in the end. Competing implementations are great but competing standards only make more work for everyone else.
The worst part is that they sabotage their good software by insisting on these bad solutions. LXD and MicroK8s for example, are distributed only as snaps - not even tarballs. LXD is actually a great software. But it's available as native package only on a few less popular distributions, and that has hurt its adoption. I wanted to try MicroK8s, but completely abandoned it due to the snap requirement.