What is the ruling on buying meat from general supermarkets in foreign countries, such as France, given the presence of Muslim-owned shops with high prices?

There is no impediment to purchasing meat from general stores in the lands of the People of the Book, based on the principle of permissibility, unless it is known that they do not slaughter according to Islamic law, such as by using electric stunning. In such a case, their meat would be considered carrion, and it would not be permissible to buy or consume it except in cases of extreme necessity. If it is merely a matter of doubt, then it does not preclude eating it, but it is preferable and more cautious for a Muslim to avoid doubtful matters and shun what is uncertain.