Right to Work Pending Outcome of EEA(FM) Application

I have returned to the UK with my non-EU spouse after having exercising Treaty rights in another EU Member State. I am a British Citizen. My spouse has applied for a residence card recently.

Regardless of EEA Family Permits, Host State RCs and short/long CoAs, what is the legal status on my spouse's right to work? My spouse intends to start self-employed activity.

It seems clear that the non-EU spouse of an EU national residing in the UK has a right to work, regardless of declaratory documentation, but is a non-EU spouse's status in any way different (legally) if they are married to a British Citizen and relying on Surinder Singh rather than simply being married to another EU national and residing in the UK?

Thanks.

As long as your SS gig passes muster and sponsor then becomes a qp in UK then spouse may go for it