printing - Hplip, succesful driver download but then fails to get the driver

I've been using different Ubuntu distros all over the last 10 years (Ubuntu, Xubuntu, Kubuntu, mint) at least.
Never asked for help once, I've always found the solutions to my problems online but this time, the fail-loop my distro went into.... this sounds a lot like a windows fail loop. Never seen a stupid fail like this one on Linux... thus I' m asking for help since I really feel like formatting my HD and quit Ubuntu for good. I'm using Kubuntu 18.04. I have a hp printer (just to be clear: this printer worked fine on Kubuntu and mint 14.04 and Kubuntu 16.04) and 18.04 came with hplip already installed. I thought this was great. The printer was able to scan with sane but there was no way of printing. I removed default hplip and installed the latest 3.19.1.
When I go get the proprietary drivers I get a "successful installation" message and right after that I get a message telling me that the driver was not installed !!!

The Gui asks me to run the driver installation as normal user and I did that but then during the process root pw is required...

is there a kind of new security center in new Ubuntu distros blocking users action like windows uac or mac OS security app?
Because I can't think of any other reason creating such a stupid fail-loop.

update, I removed 3.19 and installed hplip 3.18. I tried to download the plugin in interactive mode. Looked like it worked but after restart the device is still missing its plugin. during plugin installation I get a warning that the security key was not found for the plugin but went on installing wihtout security key. This procedure has always worked on previous distros.
I tried to manually download the plugin from hp without any success.
I looked for the plugin in hplip install folder. I found this file

hp-deskjet_1120-hpijs.ppd
this looks like the right plugin but when I try to manually install the plugin the app looks for a *.run file!!!
manual installation

https://developers.hp.com/hp-linux-imaging-and-printing/plugins
here you can find the plugin download files (all plugins)
and the god****d .asc file needed for authorising.
I'll try to do everything manually... let's see if it works

update the plugin installation is definetly broken.
I'm manually giving "hp-plugin" app the .run file it needs. I got the Key/ authorizing file but the app wants to download it from hp server. The download fails. I don't know whether the settings app fails to create the device because it misses authorization or it just can't install the plugin properly. All I know is that hplip is broken for my printer and I need my printer for working.

update, with hplip 3.18.10 I managed to succesfully install proprietary drivers.

Both device manager and kubuntu printing app are seeing the printer. neither of those app can print a test page succesfully.
Something is blocking my printer. My printer print just fine by itself. I've already printed a test page using the printer internal configuration utility.
printer stopped