In which timezone does psql display "timestamp without timezone"?
timestamp without time zone is time zone agnostic, so it is not adjusted to any time zone on display. This data type just doesn't have a time zone.
You can convert it to a certain time zone with AT TIME ZONE:
SHOW timezone;

   TimeZone    
---------------
 Europe/Vienna
(1 row)

SELECT TIMESTAMP WITHOUT TIME ZONE '2020-08-01 12:00:00' AT TIME ZONE 'UTC';

        timezone        
------------------------
 2020-08-01 14:00:00+02
(1 row)

Then the timestamp is interpreted as Viennese time, converted to UTC and displayed in my local Viennese time zone, which is offset two hours.