> The less coupled software is to hardware, the less likely it is tested in that hardware and the higher likelihood of bugs.

Yes, exactly! There are whole teams inside Dell etc. dealing with this. The term is "system integration." If you're doing this on your own, without support or chip unfo, you are going to (potentially) have a very, very bad time.

> This is not the fault of hardware makers.

It is if they ship Linux on their hardware.

This is why you have to buy a computer that was built for Linux, that ships with Linux, and with support that you can call.

Tell me how its not their fault ?

Hardware support is more than just kernel support. Additionally, not every kernel release works well for every piece of hardware. Each distro is unique and ensuring the correct software is used together to support the hardware can be difficult when you are not involved in the distro. This is why vertical integration between the distro and hardware leads to higher quality.

Firmware also plays a huge role these days (fan curves, ACPI, power management, etc.)

But saying it can vary largely by distro is overstating it by a lot. Mostly, distro issues are going to be based on how old their kernels are.

But definitely, modern hardware is much too complex to just slap Linux on Windows (and vice versa).