Turns out I also had the package + install from source. Then removed the package and tried again. What I now get on my macbook is a login window, where I put the account name and password I use to log into OpenSuse (that’s and improvement).
However, macOS tells my that login was not succesful.
journalctl -f
Dec 30 19:00:30 linux-h6ti afpd[2512]: pam_unix(netatalk:session): session opened for user thiebo by (uid=0)
Dec 30 19:00:30 linux-h6ti afpd[2512]: Login by thiebo (AFP3.4)
… seems to imply that my login was succesfull… I don’t understand…