ARK Crossplay with Game Pass or without?

If I want to play ARK on the PC and my friends on the XBOX together, do I have to get the Game Pass or is it enough if I buy the game on Steam?

You don't need a passport on the PC, you bought the game once…

And I don't know what crossplay between PC and XBox is needed, if at all…

There's no crossplay. Only via microsoft, as far as I know but not between pc steam u. PC microsoft. So the money would be waste.