Amazon retired the old Kindle for PC app on June 30, 2026, and the new Kindle Windows app in the Microsoft Store isn't packaged for ARM64/Snapdragon X devices, so the Store blocks the install on your Surface Pro. Amazon's escalation to "work with the Snapdragon format" is the right lever on their end, since packaging and DRM decisions are theirs.
Microsoft should also be working closely with major app developers to ensure that popular applications work properly on Surface devices.
Hopefully, Microsoft and Amazon can work together to provide a proper ARM-compatible Kindle app soon.