Ah, perhaps I should try this Whole Foods app. The Amazon app is very slow and requires a good data connection to launch so it's mildly inconvenient when you've already reached checkout and it won't open for you to get the QR code.

The palm thing was never prompted as part of checkout, it's true. I just did it while I was being checked out once years ago since it seemed so cool and it worked flawlessly since then. Honestly, I found the UX of it really all well done. Even if it didn't make it in the long term, I hope the team knows there were a few happy users out here!

EDIT: I just installed the Whole Foods app and it opens directly to the QR code. That's nice. It also selects the appropriate payment method. There doesn't seem to be a watch equivalent so I'll have to pull my phone out, but this definitely reduces the terrible blow of losing the palm scan. I hope it works well without good Internet access!