If you install Home Assistant Supervised on Ubuntu, the Supervisor will indicate that your system is “unsupported”. You can run an unsupported system but if you encounter a problem, there’s no official support available from the development team, only from the community. Only Debian is officially supported.
If you install it along with other Docker containers, there are some containers that Home Assistant disallows and will indicate your system is “unhealthy”. Similarly if Home Assistant doesn’t have complete control over the docker system, it will report it as “unhealthy”. When “unhealthy” it will block all upgrades to Home Assistant and prevent installing/upgrading Add-ons.