the watchtower notification configuration examples in
docker-compose.yml are not working because you have to leave out the double quotes if you define them, like this for example:
If you’re a docker-compose user, make sure to specify environment variables’ values in your .yml file without double quotes (").
We noticed this because we were not getting notifications about rocketchat updates and the watchtower docker log said that the hostname was not resolvable… which it is, when you remove the double quotes.
Ralf, perhaps you can remove the double quotes in the config examples.