Apologies, this warrants an explanation. It turns out I was wrong to be concerned. I was worried about pg_partman being able to partition by the decoded value of a column, but it already handles that quite well. From the docs (where col3 is of type uuid):
This also kind of answers your other question about your uuidv7_floor function. While not native to Postgres, the uuid7_time_encoder function used above is extremely similar to yours. See