Another update from myself...
I found a way to install skins. It does not work if you try to get new skins through the settings menues. However, if you go through the add-on browser and add them "manually" they are installed and are the selectable in the settings menues. Still does not work to add new skins through the settings menues though.
Perhaps this is something I should have tried immediately. However, having had a working system for several years where stuff like this never caused any problems I expected this to work flawlessly in a new product that is said to be better than the one i have been using. Perhaps it is better in some ways but stuff like this should work out of the box.
Still, problem seems to be solved for now (unless I find some other problems when I continue configuring the system to work as I want it to work).