Hello,
A Desktop suggestion with various independent USB controllers, an open source firmware, at least 32gb RAM and possibly a nerfable microprocessor to disable ME or equivalent.
No gaming, no hyper speed. Just working well with Qubes.
Well it seems basic requirements, but I doubt it is easy.
But three years passed and possibly even the above board or the processor changed, or something better had been released. Things change, even Taiidan disappeared from this email list.
Best
Franz