I am not sure this is the right place to post, but I find it strange that --no-local-dns does not imply --no-dns in AI. When I specify --no-local-dns, then bind9 isn't installed, but in non-interactive installation of ISPConfig (the default one), configure_dns is set to 'y'.
That's weird. Please report at https://git.ispconfig.org/ispconfig/ispconfig-autoinstaller so we can look into it.
