I have filed FB21917334, however not in a "Hypervisor Framework" category as it does not exist, only "Virtualization Framework" and didn't want to guess if it also implicitly includes the former.

TPIDR needs FEAT_FGT, which I assume is definitely supported in M2+? Are there any plans to introduce its system registers to HVF’s EL2 support?

oh, interesting. I had a feeling, but the wording of the ARM documentation was confusing. I can trap ESR/FAR by setting TVM/TRVM bits of HCR_EL2 through the register interface, but what about other standard registers, like TPIDR, ELR, etc?