Painfully encumbered with binary blobs and out of date drivers (that is, out of tree hacked in kernel drivers that will never be ported to mainline)

Linux support remains problematic.

And even Microsoft is dealing with pain points like Qualcomm he, few, and drivers actually breaking the spec and causing problems in servicing and supporting the ARM based devices.

Meanwhile properly SBSA compliant chips aren't targeted at mobile market at all and thus often lack certain features or are too energy hungry.