http://translate.nowherejezfoltodf4jiyl6r56jnzintap5vyjlia7fkirfsnfizflqd.onion/selfhosting/db/pgadmin.html
If you are on debian, everything should be in the repositories already: root@debian-pgadmin:~# apt search pgadmin
Sorting... Done
Full Text Search... Done
pgadmin3/stable 1.22.2-5 amd64
graphical administration tool for PostgreSQL
pgadmin3-data/stable 1.22.2-5 all
graphical administration tool for PostgreSQL - documentation
phppgadmin/stable 5.1+ds-4 all
web-based administration tool for PostgreSQL
postgresql-11-pldebugger/stable 1:1.0-10-g2a298eb-1 amd64
...