Success, boots and no panic so far. Attached dmesg output. Was this related to Xen lacking support for the frequency scaling features of Zen 4 CPUs or is that a coincidence?
6.13.8-dmesg.tar.gz (29.8 KB)
Edit: I saw your message on the xen-devel mailing list and subsequently noticed dom0 is lacking a /sys/devices/system/cpu/cpu0/cpufreq/ directory as mentioned here