In containers I most often see Ubuntu-minimal or Alpine.
And while Ubuntu is represented in both those groups its not clearly de facto anything.
The only place I'd personally argue you really need to run Ubuntu (unless you really want to spend time hacking desktop configuration) is on a laptop.
But even then there are a large group of people who do run things other than Ubuntu like PopOS or Mint or Fedora or whatever other new distro there is.
