Fix for White square Cursor issue in Ubuntu
if mouse cursor comes as white square in Ubuntu 24.04
then first check which mouse theme you are using; for that install gnome tweaks
> sudo apt install gnome-tweaks
Now open it and check under Appearance > Cursor
Now open file Manager and navigate to icons directory
> cd /usr/share/icons
then cursor theme sub directory ( in my case cursor theme is DMZ-Black )
> cd DMZ-Black/cursors
and run below command
> sudo ln -s left_ptr default
Your issue will be resolved