Guys, if anyone is struggling with Cross play, let me know. I have Ark on my kids XBOX 1, I downloaded the Windows 10 version on my PC (saved me a stack as I was just about to buy it on Steam). I now host a NON-Dedicated server on my PC which means I play on my PC, I send an invite to my 2 sons and they can join on their XBOX (split screen if its both of them) and it all works great!
There are a few things to know:
1. You NEED XBOX Live GOLD to join the Windows 10 server/player from an XBOX. Even if the XBOX is in the same room as the PC, there is some Cloud jiggery pokery going on so its not an internal/local LAN connection.
2. I found that because my PC (probably) has only 8Gigs of RAM, when I host NON-Dedicated Server when we fly/ride to another part of the map (Island) there are no trees, rocks etc just blank mountain with dinos roaming. When this happens I have to get my son to leave the game. I then have to exit the server and start single player (might not be required), the terrain then generates then I start Host Non-Dedicated again and re-invite him and it looks fine. He sees the terrain fine on his XBOX, its just the PC that doesn't, but if he tries cutting a tree down that isn't visible on my PC he finds the tree is just an image, he gets no resource. I'm guessing this is a server (PC) memory resource issue.
Anyway, my kids played Ark for years and I thought it looked rubbish, but now I'm hooked (graphics look better on PC, maybe its cos my screen is smaller)! Wife's not a happy bunny now we are all glued to it!