Connect to specific cluster on command line

Hi there,

how can I connect to a specific cluster on the command line, e. g. with
psql, pg_dump or pg_dumpall?

pg_lsclusters returns a list of all clusters available:

Ver Cluster Port [...]
14 main 5432 ...
14 test 5433 ...

I want to connect to or dump database xyz in the test cluster. Is it
sufficient to specify the cluster's port only?

Perl script pg_backupcluster calls psql and pg_dump with a --cluster option:

pg_dump --cluster 14/test ...

However, this option is not documented (at least I didn't find anything)
and also I didn't find anything in the sources on GitHub.

Actually, I only have the 14/main instance and cannot really test
accessing the `test` cluster. However, psql and pg_dump actually work
with --cluster 14/main and report an error when I specify 14/test so,
the option --cluster seems to work. Is it intentionally not documented?

So, whats the recommended way to connect to a specific cluster? Is it
just the port?

Regards, Carsten