When creating a private service for another instance of PostgreSQL I used the template of postgresql-15.service file installed into /usr/lib/systemd/system on Fedora 38 provided through the installation for postgres 15.3 from PGDG repositories.
There I noticed that the line ExecStart still uses the postmaster link.
I would propose to change it to
ExecStart=/usr/pgsql-15/bin/postgres -D $(PGDATA)
This change should apply also to back branches to avoid using deprecated links in PGDG software.
This seems to be necessesary on upcoming PG16.
(BTW: where is this all documented?)
Hans Buschmann