Why not just select single virtual machine configuration and make Haiku working on it? Why jump between 5-6 different platforms when even userland is not working? It makes sense to just select “virt” machine like here.
I agree that EFI is a great thing that allows unified boot process, but it is mostly useful on real hardware, not emulated. It is not required for early OS porting process. Starting EFI firmware is slow (EDK2 takes several seconds and a lot of debug output), haiku_loader.riscv finish in a less than second. Speed is important for trial and error.
It took few days for me to make haiku_loader working on bare virtual hardware, adding new boards is not that difficult.
Linux on virtual machines also rarely use EFI, it can boot form Qemu directly without boot loader by using -kernel and -initrd arguments.