Regarding Coreboot, it is far worse than that. They literally do not care anymore; focus is not on corebooting all the boards, but on serving some sort of commercial "customer".

e.g. they do seldom if ever take patches for adding support or fixing issues in older boards. They just sit there ignored.

A fork or entire new project with different focus is sorely needed.

There is also the Libreboot which may be of your interest. What I see is that there is a lot of development on Coreboot but it is indeed mostly driven by companies working on their latest platforms. There are not many contributors working on older platforms. Though in my experience the response to patches is relatively quick.