What is the ruling on individuals seeking treatment from an apostate doctor who mocks religious rituals, whether they are aware of his apostasy or not?

Apostasy is a grave judgment that should only be pronounced by well-grounded scholars, knowledgeable in the principles of Ahl al-Sunnah regarding the establishment of proof, the conditions for declaring someone a disbeliever (takfir), and its impediments. Assuming the doctor's apostasy is proven and he insists upon it, it is not forbidden to deal with him within the confines of his profession, similar to other commercial transactions. However, if there is no avenue for inviting him to the truth, it is preferable to seek medical treatment from someone else.