Raspberry Pi specifically supports Linux, and has its own Linux distro, and that is awesome.
But they have their own boot process, so the Pi support for Linux cannot be transferred to other Arm devices. And despite the good support for Linux it took them years to get 3D supported on the graphics side.
Raspberry Pi is very much an exception from the rule. But there are some others like Pine 64.
But when you move to laptops or even Arm phones or Tablets the support is abysmal, unless it SPECIFICALLY suports Arm.
Arm PC's do not have the same boot process as normal PC's and laptops, and AFAIK that already is a problem. Arm PC's are locked in harder.
On Raspberry Pi it's allowed to install whatever you want, so you can easily install your preferred distro.