Since installing timeshift, Kvantum hasn’t worked. No matter what theme I choose, I’m stuck on the default Matchama.
I’m not sure if installing timeshift was the cause, I saw that it removed some packages when I installed it and I may have also upgraded all of my packages. I’ve tried switching to testing branch, but it didn’t solve the problem so I switched back to stable and downgraded all of my packages. Your help is greatly appreciated.
I think, I had a similar problem these days and found a solution here:
https://archived.forum.manjaro.org/t/uniform-look-of-qt-and-gtk-apps/85145/14
just paste into /etc/environment
export QT_STYLE_OVERRIDE=kvantum export DESKTOP_SESSION=gnome
log out and back in again. Maybe this helps you too.
Thanks for the quick response! Sadly, this didn’t work 
I also already had
QT_QPA_PLATFORMTHEME="gnome"
QT_STYLE_OVERRIDE="kvantum"
in that file, so I don’t know what’s going on here…