pg_logical_emit_message() is how I recommend users on Postgres to implement the outbox pattern [1]. No table overhead as you say, no need for housekeeping, etc. It has some other cool applications, e.g. providing application-specific metadata for CDC streams or transactional logging, wrote about it at [2] a while ago. Another one is making sure replication slots can advance also if there's no traffic in the database they monitor [3].

[1] https://speakerdeck.com/gunnarmorling/ins-and-outs-of-the-ou...

[2] https://www.infoq.com/articles/wonders-of-postgres-logical-d...

[3] https://www.morling.dev/blog/mastering-postgres-replication-...