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Not for free (have to pay EnterpriseDB for that). Every free option here is basically "glue pieces together to build your own HA".

I am not sure exactly what Galera does, but you may want to look into Citus (https://www.citusdata.com/).

Citus is great, however do note that reading the docs you do have to change your scheme to use Citus. So it's not really "drop-in" par say.

I don't know much about Galera, but Patroni may be of interest to you

Galera is multi-master but I'm not sure that's as important with Postgres (it has good baseline performance & can fail over quickly).

Patroni is great for managing active-hot standby clusters