It depends what you mean by ‘supported’. This is a term that I often read, but it makes little sense to me.
The ‘official’ server image can be easily adapted https://wiki.ubuntu.com/ARM/RaspberryPi#Booting_the_official_Pi_2_image_on_the_Pi_3B.2F3B.2B- . You just add on the desktop of your choice. Though it’s probably a good idea to remove the cloud-image packages as they can slow boot time.
If you want to start from a clean install with your own user account then use the mini iso. This is a bit more involved on the pi AArch64 on Raspberry Pi 2 (rev 1.2), 3B, 3B+ , but mostly it is just copying and pasting instructions and not difficult.
If the above is too hard, then I made a xubuntu-core armhf image AArch64 on Raspberry Pi 2 (rev 1.2), 3B, 3B+ . This works out of the box on pi 2, 3B, 3B+. All packages used are from the official ubuntu repos.
Hope that helps!