(Solved) Mouse cursor theme problem

[kajzer]

I'm on Cinnamon, when I change mouse cursor theme the new cursors are showing only in few applications, mostly only in web browser.
For the rest cursor theme is default, I believe that's Adwaita cursor theme but I'm not sure.
The problem I'm facing is exactly the same as in this youtube video : https://www.youtube.com/watch?v=a5_WGPPMKrg
In that video there's a fix for this problem by using galternatives or update-alternatives, I believe that's a shell script from Ubuntu based systems, but I have no idea how to do that in Gentoo.
Regardless of that video, does anybody know how to fix this issue ?

Edit : Actually, update-alternatives is part of dpkg, which is available of gentoo. Anyway, I managed to solve this problem using it.