Ubuntu server itself is pretty arm friendly. But there's a LOT of software that doesn't come with the distro's packaging that one might want to run in the cloud. Docker images and vendor hosted package repos. Everyone does this for x86. Very few do it for ARM. And if you want to try to build-from-source, the dependencies of a lot of pieces are often very out of date on ARM.

There is a kind of after market ARM community that occasionally builds these items. But they are generally pretty out of date.

I don't have an issue with the base distro and what it tries to do, but there are so many random pot holes and road blocks that just don't show up for x86.

I have ARM servers running in production now. But I have workloads that aren't reasonable portable to the uArch and I don't force them there.