PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> 4. Open pgAdmin 4, connect to the PostgreSQL 13.0 server and expand the
> Databases node.
> Expected result:
> The node has [postgres].
> Actual result:
> The node has [postgres] and [template1].
There's no particular concept of a "system database" in Postgres,
so I don't know what pgadmin is doing to decide which databases
to show or not show, but evidently it's not too well thought out.
(The closest concept I can think of is whether a DB is marked
datistemplate, but a test confirms that pg_upgrade successfully
preserves that property on template0 and template1.)
I'd suggest you file this complaint on the pgadmin lists.
regards, tom lane