phppgadmin "login failed" between containers

Trying to enter the correct user and password set for the database fails with the extremely helpful error "login failed". As listed below, I have tried all of the common solutions for this issue as found around here, no dice yet.

• Containers are on the same network.
• The database port is the default, and is forwarded.
• Can ping between containers from within.
• Can login to Postgres using psql from the HOST machine and within database container using credentials below.
• Verified the value of show listen_addresses; is "*".
• Watching the log output of Postgres does not show any messages releated to connections when attempting to login using phppgadmin, or errors.
• Provided recommended and required environment variables to the containers.
• I have tried changing the forwarded port of the database container and then changing PHP_PG_ADMIN_SERVER_PORT, no difference.
• netstat confirms the database is listening on the right port on the host.
• I have rebuilt the containers many times, including deleting Postgres' data folder.
• Just in case something was off with automatic name resolution, I tried manually substituting the docker IP address of the database container in PHP_PG_ADMIN_SERVER_HOST.

docker-compose.yaml

networks:
  centurion:
    name: centurion-net
services:
  benard:
    image: postgres:latest
    restart: always
    volumes:
		- /opt/containers/benard/persist/data:/var/lib/postgresql/data
    environment:
		- POSTGRES_DB=pg
		- POSTGRES_USER=pg
		- POSTGRES_PASSWORD=password
    ports:
		- "5432:5432"
    networks:
		- centurion
  benard_ui:
    depends_on:
		- benard
    restart: always
    image: dockage/phppgadmin:latest
    ports:
		- "8200:80"
    environment:
		- PHP_PG_ADMIN_SERVER_DESC=BENARD
		- PHP_PG_ADMIN_SERVER_HOST=benard
		- PHP_PG_ADMIN_SERVER_PORT=5432
		- PHP_PG_ADMIN_SERVER_SSL_MODE=allow
		- PHP_PG_ADMIN_SERVER_DEFAULT_DB=template1
		- PHP_PG_ADMIN_SERVER_PG_DUMP_PATH=/usr/bin/pg_dump
		- PHP_PG_ADMIN_SERVER_PG_DUMPALL_PATH=/usr/bin/pg_dumpall
		- PHP_PG_ADMIN_DEFAULT_LANG=auto
		- PHP_PG_ADMIN_AUTO_COMPLETE=default on
		- PHP_PG_ADMIN_EXTRA_LOGIN_SECURITY=false
		- PHP_PG_ADMIN_OWNED_ONLY=false
		- PHP_PG_ADMIN_SHOW_COMMENTS=true
		- PHP_PG_ADMIN_SHOW_ADVANCED=false
		- PHP_PG_ADMIN_SHOW_SYSTEM=false
		- PHP_PG_ADMIN_MIN_PASSWORD_LENGTH=1
		- PHP_PG_ADMIN_LEFT_WIDTH=200
		- PHP_PG_ADMIN_THEME=default
		- PHP_PG_ADMIN_SHOW_OIDS=false
		- PHP_PG_ADMIN_MAX_ROWS=30
		- PHP_PG_ADMIN_MAX_CHARS=50
		- PHP_PG_ADMIN_USE_XHTML_STRICT=false
		- PHP_PG_ADMIN_HELP_BASE=http://www.postgresql.org/docs/%s/interactive/
		- PHP_PG_ADMIN_AJAX_REFRESH=3
    networks:
		- centurion

If you docker exec into the phppgadmin container and try to connect to postgres with the psql command, you'll see:

psql: SCRAM authentication requires libpq version 10 or above

And originally I was going to write about how to configure recent versions of Postgres to use md5 authentication instead, but then I discovered that was pointless:

The version of phppgadmin in the dockage/phppgadmin image only supports Postgres up to version 12. Using anything more recent results in the error message:

> Version of PostgreSQL not supported. Please upgrade to version or later.

It looks like that image was last updated over four years ago, so you may want to find a more recent alternative (or build your own).

With the above limitation in mind, a working configuration looks like this:

volumes:
  postgres_data:

services:
  postgres:
    image: docker.io/postgres:12
    volumes:
      - "postgres_data:/var/lib/postgresql/data"
    environment:
      POSTGRES_USER: "$POSTGRES_USER"
      POSTGRES_PASSWORD: "$POSTGRES_PASSWORD"
    command:
      - postgres
      - -c
      - log_connections=on

  phppgadmin:
    image: docker.io/dockage/phppgadmin:latest
    environment:
      PHP_PG_ADMIN_SERVER_DESC: postgres
      PHP_PG_ADMIN_SERVER_HOST: postgres
      PHP_PG_ADMIN_SERVER_PORT: "5432"
    ports:
      - "8000:80"

Assuming that I have the following .env file:

POSTGRES_USER: postgres
POSTGRES_PASSWORD: secret

Then I can docker-compose up, connect to http://localhost:8000, and login as user postgres with password secret.