Icons don't show up in Kubuntu (Ubuntu 23.04 lunar)

[Roon]

I downloaded the grub-customizer-5.2.3 source code and followed the instructions for make + install

It seems to install successfully, but on opening the app, the icons for the menu doesn't show up

Also I am not sure if the app has a hard theme, in which case, it wasn't respecting the system's dark mode preferences either

My system details:

OS: Ubuntu 23.04 lunar
Kernel: x86_64 Linux 6.2.0-24-generic
Shell: bash 5.2.15
Resolution: 3840x1080
DE: KDE 5.104.0 / Plasma 5.27.4
WM: KWin
GTK Theme: Breeze [GTK2/3]
Icon Theme: breeze-dark
CPU: Intel Core i5-8300H @ 8x 4GHz
GPU: NVIDIA GeForce GTX 1050 Ti