In order to do that you will need to un-load the font awesome icons from loading. You can do that by simply add the following line (also documentation for it):
$crud->unsetCssIcons();
With this you un-load the font-awesome icons and you can add your own implementation of font-awesome. You will need to make sure that you have loaded the CSS version of font-awesome 6.
If you’ve downloaded the Pro files directly, include the CSS file from your local setup. For example:
And this should work. I am not sure about the details of how to download the assets from font-awesome 6 but I guess this article could be a good starting point: Use a Kit | Font Awesome Docs
I set $crud->unsetCssIcons(); as your suggestion but is not working as expected.
I am using Metronic Template to build my backend. Fontawesome 5 (build into metronic’s source)brand icons are displayed correctly were I am not using GC but when I had GC this icons are not displayed.
Look at my attachment. (Black brush tape private info and red brush is to show that Fontawesome is displayed outside GC)