arm64 Hyper-V mandatory fallback shielding happens only on b226xx. On b22000, b26x00 and b28000 it works fine. arm64 Hyper-V mandatory hypervisor starting happens only on b26x00 and newer, but you need the hypervisor thing anyway to start vm (there is no alternative to it at arm64). On b226xx and older you can actually stop hypervisor.
Funny story of PC amateur: On x64 and x32 PC I sometimes disable hypervisor layer in Windows 11 to make VirtualBox run faster directly accessing VT-x/AMD-V. So on arm64 I worked hard to be able to disable hypervisor in Windows 11 (it is a real challenge). So after success I run VirtualBox arm64. Yeah, it will run faster directly accessing xxxxxxx(analogy), right? Well, it doesn't run at all. There is no xxxxxxx(analogy).
Hello again and question again: Is it possible by any way to do the upgrade from 25H2 x64 to 26H1 x64 (= not clean install) and bypass CPU, TPM and SecureBoot check on real PC? IMHO SecureBoot can't be overriden in registry.