at least grammatically

I offer a nit to pick. The collocation local congregation is perfectly grammatical. It may suffer from some logical or semantic problem, but I think not. Having looked over a couple of dictionary entries, I can see nothing which specifies that a congregation must be local to the speaker. It's simply an assembled group of people. And how would one speak of distant congregations to which one did not belong?

Etymologically, the word is interesting in its derivation from the Latin grego, gregare, 'to assemble' from the noun grex, gregis, 'herd, flock', cognate (link) with English cram and Greek αγορα (agora). Interesting distinction in English in the positive versus negative connotations of herd and flock; cf. sect, cult, and religion.

Ceci n'est pas un seing.