Is Yunohost compatible with the A64 OlinuXino?

I don’t see an image available.

Not it’s not, because we don’t build the package for arm64 (which is the architecture of this board, if I remember correctly)

There’s probably not good technical reason for this (we probably just didn’t have time and hardware to test that) but if you know your way around debian packages, you might me able to build packages manually…