First off Debian can be run headless as well so that’s a moot distinction.
But if you already have Ubuntu running HA then I wouldn’t mess with it and just go from there. If you are using the machine for anything other than just running HA the you are already not “officially supported” anyway.
The “it’s not officially supported” thing sounds way more ominous than it actually is. I’ve been running HA now for over 3 years and have only asked for “official support” a few times. Two times were on the discord channel and it never helped me at all either time. I suppose you could get “official support” by submitting bug reports when you find them but I typically don’t find the bugs soon enough to have needed to do that aside from a few times and unless a lot of people are experiencing those same bugs it won’t get touched either.
Most of the support you will get is going to be from people here on the forums.
The bottom line is stay with what you have and you’ll likely be fine for a long time to come. And if you get into trouble come here and ask (after doing your own research a bit to see if it’s already been asked/answered first of course ).