In Postgres 10, how do the choice of SERIAL or UUID type as primary key affect replication, if at all?
that claim seems spurious.

I do integer IDs with multi-master replication, it's not hard.

I set the step of the sequences to such that two servers cannot use the same id number.

alter sequence foo_id_seq set increment_by=10;
select setval('foo_id_seq',2);  -- or 3 or 4 etc...


but if you can do it natural keys are even easier to replicate.