That’s not what AMD and Intel does to get their hardware to work on Linux.
They focus on upstreaming the codes needed for the hardware to run in want Linux distro.
By sponsoring 1 distro who does not really care about upstreaming is not helpful.
Why is Radxa giving up on software support?
Of course mainlining the stuff would be the best option but this would trickle down to armbian as well as everything else.
Yes ofcourse but it is the responsibility of the vendor. Either chip or device vendor.
If device vendor are ready to pay for device support at OS level they should just pay to upstream device support so os maintainer does not have to do much.