i dont know how to open kvantum im on plasma 6 and ive alrdy copied this libsForQt5.qtstyleplugin-kvantum in my system pkgs or smt
libsForQt5
is ONLY for Qt5 packages. Plasma 6 uses Qt6 only. Instead, use kdePackages
for all packages of that group. This prevents a lot of issues.
So in this case
kdePackages.qtstyleplugin-kvantum