Found that post I was talking about: Dom0 Security - #2 by Sven
The Qubes OS project is actively working on moving more of the hardware handling into dedicated qubes: sys-net, sys-usb, sys-audio, sys-gui, etc. Once this is isolated in a qube you can choose which distro to use.
That been said, this is from June '22, and discussions regarding this are at least from 2016.
Hopefully, the ability to choose the dom0 distro will be prioritized to minimal build specific to Qubes OS or even more shady Qubes air.