Fragmentation in the non-x86 world really hurts adoption. RPi presents a very well documented configuration that can be used as a target for development.

RISC-V is going through this exact same problem right now. All of the current implementations have terrible documentation, and tailoring Linux for each of these is proving to be difficult. All of these vendors include on-board devices that have terrible doc and software support.

ARM has a mitigation for this called SystemReady. It's basically "does your board support UEFI enough to usefully boot a battery of generic ARM Linux images". The Raspberry Pi can be made SystemReady, and Radxa also makes SystemReady-compliant SBCs you can buy.

RISC-V would do well to adopt and promote a similar spec.