Criteria for Qubes OS certification are described in Hardware Certification Requirements section. We discussed those criteria with Marek (Qubes OS maintainer) during Qubes OS minisummit 2019 slides can be found behind the link.
In general, it requires providing to Qubes OS team hardware for the validation of new OS versions and get to an agreement about the cost associated with the verification process.
As it is stated on the website:
The only exception is the use of (properly authenticated) CPU-vendor-provided blobs for silicon and memory initialization (see Intel FSP) as well as other internal operations (see Intel ME).
So some blobs can be included in firmware and that does not cause problems with certification. In the case of the Intel sensor hub, I’m not aware of an open-source alternative and we will probably not see it until someone will abuse sensor hub firmware obscurity.