> Initial experiments show no observable problems when copying PGDATA or in fact using physical streaming replication between the two CPU architectures.
That's an interesting result. The topic of physical replication compatibility interested me much back in 2017 and I raised this question on PGCon [1]. As I recall the compatibility is not guaranteed, nor tested, and not going to be, because the community doesn't have resources for this. The consensus was that to migrate without downtime the user has to use logical replication. Thus what you observe should be considered a hack, and if something will go wrong, you are on your own.
Of course, there is a possibility that something has changed in the past four years. I'm sure somebody on the mailing list will correct me in this case.
