Alt RPM Distro (CentOS?) in dom0

And aside from being shiny, what does Yocto or Alpine do that CoreOS doesn’t?

Again, I am not an expert. But the point as I understand it is the
reverse of your question. The goal would be a dom0 that is extremely
minimal, which means: reduced attach surface.

Currently we need a distro in dom0 because the GUI lives in dom0. Once
that is no longer the case, there should be no reason left for any user
to interact with dom0 in any way. There shouldn’t be anything anybody
would want to install, configure or maintain in dom0. It should just be
the Kernel, XEN and Qubes daemons.