We faced this migration, too. My sympathies. Adding to your list of options that still require _some_ downtime: we used Bucardo [0] in lieu of logical replicat

We faced this migration, too. My sympathies. Adding to your list of options that still require _some_ downtime: we used Bucardo [0] in lieu of logical replication. It was a bit of a pain, since Bucardo has some rough edges, but we made it work. Database was ~2 TiB. [0] https://bucardo.org/ https://bucardo.org/