See: https://www.pgadmin.org/download/pgadmin-4-apt/
#
# Setup the repository
#
# Install the public key for the repository (if not done previously):
curl -fsS https://www.pgadmin.org/static/packages_pgadmin_org.pub | sudo gpg --dearmor -o /usr/share/keyrings/packages-pgadmin-org.gpg