Thanks for the tip with root applications. That pointed me in the right directions. Here is what i did.
- Gparted
- Gnome Software
- edit gsettings with dconf editor
- it’s still only adwaita but i’m okay with that
- Qmapshack
- activate ‘QT_STYLE_OVERRIDE=kvantum’ in
/etc/enviroment
- Flatpack
- give all Flatpak packages permission to access ~/.themes and ~/.icons
- tell Flatpak apps which theme/icon to use with Flatseal (GUI Method)