The main issue is that what's upstreamed is essentially drivers for the SoCs - but the firmware of Qualcomm-powered laptops tends to be not fully compliant. So

The main issue is that what's upstreamed is essentially drivers for the SoCs - but the firmware of Qualcomm-powered laptops tends to be not fully compliant. So it's easy to make a device powered by one when you control how linux is booted on it, but for whatever reason things like EFI NVRAM interface on windows qualcomm powered laptops was done non-standard and the only reason windows works is because there are drivers shipped which work around it - and I seriously doubt its intended by Microsoft, because Microsoft actually benefits from devices following their official, documented, hardware-interface specs - it makes for easy upgrades, reinstalls, etc. etc.