Eating meat in Halacha and Hashkafa; is vegetarianism a treif Hashkafa?

Is it permitted to be a vegetarian or vegan? What about an animal rights activist? Is meat required on Shabbos, Yom Tov and at a Bris? Can we eat veal? Is there a chance shchitah can be banned in the U.S. like what’s happening in Europe? Is synthetic meat still fleish? Can an Ashkenazi eat meat from a Sefardi hashgacha and vice versa? Can meat be left alone on a barbecue or at home with non-Jewish cleaning help?