So far it appears that Huawei is the only Chinese firm producing chips on 7nm; while western commenters have stated that it is a SMIC process - I don't actually think they know for sure as none of these companies have made it official - in other words the process may be proprietary to Huawei.

However 7nm is in volume production at a level so high that can do non-critical projects such as the Mate 60 phone rather than just the stuff where all imports to China are sanctioned (high-end AI chips, chips for spacefaring, and military).

Likely other sanctioned Chinese chip designers will use the process as it appears that Chinese authorities want internal competition rather than just have one single dominant company (Huawei).