I'm sure this has already been talked about but just in the off chance it hasn't--I found an work around to being able to invite friends for Alt/Match Play etc.
Make sure the friends who you want to invite have tee'd off on some course in stroke play single player (practice or ranked) and then you can create a game, click invite, put their full name in the search box and they will get the invite.
Like I said, my guess is this has already been talked somewhere on here but thought I'd mention it even if I was being redundant.