I was born in Tatarstan. For us, the division was Christian or Muslim. “Christian” was assumed to be Orthodox, but Catholics were considered to just be a kinda weird foreign flavour of Christianity. Pretty much everyone else made their presence known by proselytizing, and thus earned the title of sectarian for being a crazy evangelist (a chill immigrant who happens to be a Buddhist or Anglican doesn’t really talk much about their religion, so thus the only small religions you notice are the ones headed by people who don’t mind their own business).