It's pretty easy - and not. Simply add fa fa-home to menu item > Link Type > Link Class, and you got your icon in front of your item.
What is a problem is that the font following refers to Font Awesome (serif font) and there is no space between the icon and the item.
Any idea how I can add the icon with space and without referring to the serif font Awesome font?
I've tried this in Menu Item > Link Type > Link Class:
fa-home --> nothing shows
fa fa-home --> icon shows, no space between the icon and the link + serif font
fa fa-home [&nb sp;] --> icon shows, no space between the icon and the link + serif font
[&nb sp;] = no break space
after the icon? – Mythic Jan 24 '19 at 4:31