How about
sudo pacman -Rdd garuda-mate-settings
then
garuda-update
since garuda-mate-settings is just a pkgbuild file used to create dependencies to bundle packages and make installing them easier you can forcefully remove it and still have all it’s installed “dependencies” available in your system and not be affected in anyway.
Or, you can wait it out until nico or whoever maintains this meta package updates its dependencies since kvantum-qt5 has been renamed in the repos so you won’t find it with that name anymore.