Running Arm64.aarch64 FreeBSD on QEMU/UTM.app on Apple Silicon

That sounds like Hypervisor.framework (hvf) not Apple's virtualisation framework, which is independent.

UTM does "already" if you enable "Use Hypervisor"

Before macOS 14, Virtualization framework required bare linux kernel file and initrd to load Linux. I'm not sure if that format is compatible with other systems.

Since macOS 14 you can actually specify ISO file instead. So it makes sense to try out other operating systems.

Anyway there's very little flexibility in virtualization framework. So if one would want to build a proper virtualization solution to support multiple operating systems, Hypervisor framework would be more appropriate. Of course it's low level.

With virtualization framework one can't even provide support for custom storage formats like qcow2. It's very bare-bones.

UTM supports this, you can choose Apple virtualisation instead of QEMU when creating the VM

QEMU uses the Hypervisor framework just like Virtualization does.