PS Store showing Returnal Digital Deluxe Edition as PS4 compatible just because it has a digital soundtrack that you can play on a PS4. The game itself is not playable on PS4. :
PS Storeにてサマーセール開催! PS5「Returnal」が43%オフに - GAME Watch
Returnal - Exclusive PS5 Games | PlayStation (US)
Buy Returnal - PS5™ Disc Game | PlayStation® (US)
Browsing the PS store late at night, saw the trailer and preordered the deluxe edition. I am so hyped! Why isn't this game more advertised? : r/ Returnal
Returnal Review: A gorgeous, incredible game you should not buy – I Need Diverse Games