It's pretty slow to load compared to GRUB without any theme, but maybe that problem is caused by my DELL laptop.
I saw that a fast flash drive with YUMI was always slow navigating in the menu on my laptop but faster on another laptop
I have Installed it in on Kubuntu 20.04 with GRUB Customizer, but the icon for Kubuntu is wrong, it's displayed the orange one Ubuntu instead of the blue one of Kubuntu.
I thought first that the problem might be that the theme doesn't have an icon for Kubuntu but it has.
Then I thought that the problem could be from the string 'Ubuntu' that is used as the GRUB menu entry even for Kubuntu, so I renamed that from the same tool from Ubuntu to Kubuntu, but the icon is still the wrong one.
If I could fix this then everything would be great, but I have no more ideas what to try.