Why is there so little interest in ARM-based Linux laptops? Does AMD (or Intel) have anything even close in performance / watt that one can get from an ARM-based system?
AMD and Intel both have processors that perform much better than anything ARM-based except Apple's M1 processors (which of course nobody else has access to). That might change once Qualcomm release the new design they are supposedly working on, but that's not available yet.
I think Apple's chips aren't that far off being twice as fast as Exynos chips in single-core performance. Whereas the latest AMD and Intel chips are more or less on a par.
ARM-based laptops are definitely more niche and if you don't have a large company like Apple forcing the adaption, you'll have a hard time to support proprietary software, including stuff like drivers. It would absolutely be cool to have an open ARM-based high-end laptop, but it's not drop-in like AMD.