nextcloud and Docker and reverse proxies

I have a nextcloud setup like described here (docker-compose, let’s encrypt proxy companion, postgres and nextcloud). And for a while I couldn’t connect any new nextcloud clients to the installation.

This fixed it:

<?php
$CONFIG = array (
  # manually added because it's not picked up from
  # the env vars once set ... it seems ...

  # the docker IP range
  'trusted_proxies' => ["172.16.0.0/12"],

  # the hostname of the server
  'overwritehost'   => "my.super.secret.server",

  # the ENDUSER->PROXY protocol, NOT the proxy-> nextcloud protocol!
  'overwriteprotocol' => "https",

  #
  # AAAND NOW back to the original config file ...
  # ...
)

Some notes: