First of all, you need to run this script as root, so the script can make changes on your /usr/share/applications folder. If you want to change the Lunar Client icon, just delete the lunar-client.png to your custom one, with the same name before running the script.
As said before, run all commands with sudo to prevent erros!
And do not forget to install LunarClient AppImage from the official website, and rename it to LunarClient.AppImage so the script can find it automaticaly.
git clone https://github.com/KarboXXX/lunar-client-search.git
cd lunar-client-search
For now, as it not requiring any python3 packages that are not default, its non existent and requirements.txt file, so run it as normal using python3 lunar.py
I had nothing better to do, and its 05:36 AM here in brazil as now, and i have insomnia.