You realise Debian is the base distribution?
Ubuntu takes 6 monthly cuts from Debian Testing, adds some in house stuff puts them through QA and performs a release.
Linux Mint is produced by Cinnamon devs, similar to KDE Neon. They take the last Ubuntu LTS, remove many of the in house additions, add the latest Cinnamon desktop and release.
Cinnamon got upstreamed into Debian to make the process easier.