I could make a qcow2 image, but it's pretty easy to install. I was eventually able to get network and audio to work by making audio load after network initialization. I put a domain xml file and some other bits with an explanation here:
https://github.com/jmontleon/libvirt-configs/tree/main/MorphOS

Pegasos 2 requires, or at least works better, with an actual firmware you can grab from the wayback machine. There's no nvram so you need to get on the serial console to boot MorphOS, so I strung together a qemu hook, systemd user service, and expect script to do it for me so it's like a typical experience.

I created an issue here regarding the audio/network issue, but as of yet I don't think there's much idea what's going wrong. https://osdn.net/projects/qmiga/ticket/48376. (osdn.net has been loading terribly slow so it may take a few tries to load the page)

Performance is mediocre. Generally the system is usable and responsive. I managed to get some audio to play once or twice from youtube videos, but browsing youtube.com or m.youtube.com is excruciatingly slow.