The problem isn't support for the ARM architecture in general, it's the support for this particular board.
Other boards like the Raspberry Pi and many boards based on Rockchip SoCs have most of the necessary support mainlined, so the experience is quite painless. Many are starting to get support for UEFI as well.
I believe some other distros also have UEFI booting/installers setup for PI4 and newer devices because of this, though there's a good chance you'll want some of the other libraries that come with Raspberry PI OS (aka Raspbian) still for some of the hardware specific features like CSI/DSI and some of the GPIO features that might not be fully upstreamed yet.
There's also a port of Proxmox called PXVirt (Formerly Proxmox Port) that exists to use a number of similar ARM systems now as a virtualization host with a nice ui and automation around it.