Font Awesome plugin

Is there a simple way to add Font Awesome icons in a selectfield to Kirby 3?

I personally don’t know of any plugin for Kirby 3 yet. There were some solutions for Kirby 2: Custom field - Font Awesome Icons

You could however simply use a json API for the select options:
Googling “fontawesome json” will surely get you a nice list of the icon names for your version.

Everything else, like displaying the icon after selecting it, requires a custom field.