I'm having trouble getting the window theme to appear as the system theme on my installation of Zorin OS. I've made sure Steam's flatpak has theme and icon directory permissions (verified with other flatpak apps) as well as used GE-Proton and configured GTK themes using protontricks. Nonetheless, the window theme hasn't updated. When I was running Cinnamon, Proton seemed to use my system theme without any configuration, so I'm not sure what's going on here. Any help would be appreciated.

Image of what I'm talking about:
https://imgur.com/a/OcADvo8