Risk of Rain 2 platforms include current stores plus a narrower future DLC list. Hallowed Concepts is PC, PS5, and Series only per the collected notes.
Risk of Rain 2 platforms and "where new content still ships" are no longer the same table. The source confirms upcoming fourth expansion Hallowed Concepts only on PC, Xbox Series S/X, and PlayStation 5, and explicitly not on Nintendo Switch, Xbox One, or PlayStation 4. Epic store copy in the notes marks that expansion Coming Soon on Windows. Price is unannounced. A collected wiki excerpt guesses the same $14.99 band as prior expansions; that is "most likely," not an official price, so it stays unverified.
Which stores sell the base game today is not listed line-by-line in the source notes. The platform sentence this page can stand on is the Hallowed Concepts window.
How to answer PS5 searches
The keyword list is full of PS5 / Xbox questions. What we can say: PS5 and Xbox Series are on the future-content list. PS4 and Xbox One are on the "no more new content" list. Whether PS5 and Xbox can share a lobby is not in the source; see the crossplay page.
Keep Returns separate
Risk of Rain Returns is another product. The source only mentions it when comparing environments (Damp Caverns, Lynx Tribe). Do not reuse Returns store lists as Risk of Rain 2 platforms.