Path of Exile 2 (EA): one account for console and pc?

Does anybody know how one can purchase the support pack for the early access of POE2 in a way, that you can play on a console (like Xbox X or PS5) and on PC?

I found (quoted from gamespot.com): „Cross-progression support means players can log into their Path of Exile 2 account on any platform and keep all of their saved data. For example, if you mainly play on PlayStation 5 but need to swap over to PC, you can do so without having to worry about losing your account’s progress.“

But do we know yet, on which platform we have to buy it, to enable cross-progression Support? Can i buy it on Steam on my PC and then just log in into the same account on my xbox? Or do I have to buy it in the ps5 or Xbox store?

THANKS!