Fresh install - admin cannot sign on

After three years of nextcloud, I’m still only using the filesync. Maybe it’s time to move away from bloat …

So I spun up the docker-compose.yml from the server manual. The only things I changed were the passwords and the email address (as per the documentation).

When I typed the ip into the browser, it got redirected to path /accounts/login/?next=/ and the sign-on page appeared. Horray!

Unfortunately, the admin email address and password from docker-compose, was rejected from signing on (Incorrect email or password).
So I tried the Forgot password? link and got:
Failed to send email, email service is not properly configured, please contact administrator.

Could someone help me with the fault-finding? Again, I deployed the yml file as-is.
This is on a Debian server.

Here is a generic answer, that can help:
You may need to enter the docker container and execute the script in the respective seafile folder.

I’m also seeing this but no luck with the rest admin script, any other thoughts?
Ended up posting here