Do we have board schematics available for the ROG Ally?

Typical asus denying warranty claims. They are in a lot of hot water lately for this varry issue.

yes schematics do exist out there availability is incredibly limited as it is a copyrighted document and those who do have essentially pirated you can to it if you know where to look.

Openly disturbing proprietary engineering Cad documents is usually met with legal action against the the distributor(s) from the manufacturer.

This is why most of these schematics aren't on the open web or come from pay walled forgien software companies located in places that do not respect United States law like China , you might have some luck with the European union as they have passed bills on right to repair making technical documents and diagnostic software tools required to be made available. However these laws haven't been fully implemented yet and I don't think manufacturers of consumer electronics are having this legislation enforced against them yet.

You can always try to figure out who was on the engineering team for any given device and ask them very very nicely and expect and accept a firm no.