Where did you see that the initial setup script was still using "openvasmd --list-users" ?

The current version of the openvas package (8.0) correctly uses --get-users:
$ grep openvasmd /usr/bin/openvas-setup
openvasmd --migrate
openvasmd --rebuild
if ! openvasmd --get-users | grep -q ^admin$ ; then
openvasmd --create-user=admin

Please report me the version that you are using with "dpkg -s openvas|grep Version".

Hi.

dpkg reports that I'm using ver. 8.0

I've tried an openvas update with a clean Kali linux and now it seems to work, so I suppose I had a problem when I updated.

Thank you for your support :)