I am using Xbox with a totally different email than my bf who uses PC. We try adding each other but neither of us get the friend request.
However, I was able to friend his nephews account on PS4. So we are able to cross play together when his nephew is on, though when its just us, we can't add each other, so therefore unfortunately we can't cross play without his nephew on. I feel like its a bug in the system, and the only work around is if we join through a PS4 account. So Xbox and PC can't add each while PS4 and PC can, then PS4 can add PC/Xbox users. PS4 seems to have the luck in early beta. Hope there is a work around, or fix soon!! Crossplay definitely has been slightly buggy yet seems to have slightly improved since starting. I will patiently wait, tho eager to play duos with my man!!
Hope this helps anyone who relates!!