Make sure PSQL is binding to an externally accessible interface. Modify /etc/postgresql/15/main/postgresql.conf to change listening addresses
listen_addresses = '0.0.0.0'Add the remote server(s) that will need to connect (read the notes in the file) to /etc/postgresql/15/main/postgresql.conf
host <database-name> <db-username> <remote-host-subnet> <auth-method>
host myApp myAppRW 10.0.0.0/28 md5Restart PSQL