It looks like postgres falls back to default port (5432) if port is not
specified in postgresql.conf.
The probles is actual in postgresql-common=191.pgdg14.04+1
Unfortunately, pg_upgradecluster does not handle this situation. It fails
with "Error: could not get cluster locales" and such message hardly helps
to debug the problem.
Could you, please, take a look?
Best regards,
Yuriy.