Xen is available for ARM but not for Power9… It is possible to port Qubes for ARM but I’m not sure about performance and also I guess the Qubes team has limited resources and need to focus on the largest population, which is x86 for the foreseeable future. I personally would love to try Qubes on Power but do not believe it will ever happen. Power is for niches like large in memory DBs, AI, HPC and not desktop use, although you can use it as your personal computer.