IMO, event this is ever supported, you still should migrate using a Dump, or proper synchronization service
A dump and restore is simply not viable for a database of any size. 100GB datababase which is not at all in the "large" territory would be down for at least an hour if not longer.
Pg_upgrade is generally the right shape of thing for this problem. One could debate whether replication is a better approach for even reducing that down time. (Pg_upgrade is on the order of minutes, it is not a size of data operation but rather a size of catalog operation). But that dump/restore is acceptable and the best option isn't really the case these days.
In that case as long as the source has some form of decoding (test decoding plugin or pgoutput) it should work.
That a dump is always the best process anything isn't really true these days (I know someone will show up with a case of why dump is 100% for what they need in moving data around). But, the combination of logical decoding, and pg_upgrade cover most cases.
Admit I was jumping a bit with upgrades, but that is where dump/restore does most often come up, not with migrations.