PBI from Peter Pig isn't squad level, the game works with one company per player, but the rules are simple enough that I use them with a school club.
In part because the game works with squares, so no arguments over measuring ranges or measuring movement, also no arguments about cover - squares are open, partial-cover, or heavy cover. Whatever cover is in the square, any figures in that square are in it.
There is a free test version (PBI quick start) which has the basics:
https://www.peterpig.co.uk/rules.html