polkit not working properly in KDE Plasma

[OrcLex]

Kubuntu 19.04
Plasma 5.16.4
polkit 0.105-25

Hi,

I'd like to configure polkit to allow normal users changing their SDDM Login Screen without asking for a password.

Up to 0.105 polkit should use .pkla files and hence I created /etc/polkit-1/localauthority/50-local.d/50-user-sddm.pkla containing

[users are allowed to change sddm background or theme]
Identity=unix-group:adm;unix-group:users
Action=org.kde.kcontrol.kcmsddm.save
ResultInactive=no
ResultActive=yes

Of course the user is in the group users but I still get an authentication required dialog when clicking on apply. I'm sure this was working some time ago...

A quick test shows me that other rules for gnome software are working and for example gparted opens without asking for an authentication:

[users are allowed to start gparted without authentication]
Identity=unix-group:adm;unix-group:users
Action=org.gnome.gparted
ResultInactive=no
ResultActive=yes

So polkit is running.

If I change the action policy directly in /usr/share/polkit-1/actions/org.kde.kcontrol.kcmsddm.policy
and change

 <allow_active>auth_admin_keep</allow_active>

to

<allow_active>yes</allow_active>

it is working and I can change the sddm theme without a password. But this file will be overwritten on updates and this xml file looks for me to a newer polkit configuration file using .rules instead of .pkla files. It should go to /etc/polkit-1/rules.d and hence I created a file in rules.d with

polkit.addRule(function(action, subject) {
if (action.id == "org.kde.kcontrol.kcmsddm.save") return polkit.Result.YES;
}
});

for a newer polkit but it is still ignored.

I'd like to change some more polkit configurations like org.freedesktop.packagekit.upgrade-system for users to update...
Does anybody get polkit running for any KDE Plasma configuration?

Thanks!