It seems like there aren't as many cards on the auction house compared to what I would expect. If I toggle cross-play on, will I see Xbox cards listed also? I imagine now I'm only seeing PS5.
No, auction house is platform specific. Turning on cross play won't change anything. Additionally, current gen and old gen no longer share a marketplace. So ps5 now only sees ps5 cards while previously it would see ps4 and ps5 cards. This is probably the reason you see less cards than you expect. The standard edition also hasn't come out which may also have an effect.
Unfortunately nope. It's completely divided. Last couple madden's shared the AH between console generations, but xbox and play station have always been separated. Now it's completely separate. Xbox one has their own, xbox series x it's own, ps5, ps4, ect. It's low cause there's not much to do with the ealy access so not many people on ripping packs. It will pick up this weekend