What will Stingrays do if a mobile device uses Starlink? There's no way the Feds are going to lose this ability to deploy Stingrays once Starlink Mobile comes around.
Stingrays don't care where the provider's towers are, they work by pretending to be their own, and (ideally for you if you are the person wielding one) causing your target's phone to connect to or through your antenna. The only way Starlink would help a target is if your phone rejects tower signals that are not mostly above you, or if Starlink Mobile would utilize something other than the 3GPP standards, both of which are unlikely unless they want to sell their own fully proprietary phones.
Do you think that Musk wants to become the dominate global cell provider and does NOT plan to use that information collection capability to enable his friends and hurt his enemies?
Probably the feds will just ask Starlink for the triangulated coordinates of their person of interest.