THE ANSWER
Xbox lists Series X|S, Windows PC and Steam. Xbox Play Anywhere is advertised for eligible Xbox digital purchases, with shared progression across the supported Xbox and PC versions.
Buying a copy and playing together are separate checks
Do not assume a Play Anywhere purchase provides a Steam license. Likewise, available versions do not by themselves establish every crossplay combination.
No PlayStation release is established by the official sources used for this edition. Check current publisher announcements before making a platform purchase.
Make a platform list for your squad
Kingy preparation advice · not a tested gameplay procedure
Write down the device and storefront each person intends to use. Then verify game ownership, online access, unlock date and the supported method of playing together.
If any one of those remains unclear, resolve it before the group commits to buying extra copies or subscriptions.