> not having straightforward APIs like BIOS/EFI.

Oh, no, not this again!

> But we generally see that as soon as the manufacturer stops their updates, the community versions start lagging behind as well.

Care to demonstrate that?

The reason OpenWrt abandoned most routers was

1) insufficient flash space in the kernel partition, or insufficient total flash space in no-USB, no-SPI routers,

2) unwillingness to repartition flash because it breaks compatibility with official firmware (as if anyone installing OpenWrt would care),

3) insufficient RAM to run newer kernels

and, most importantly,

4) unwillingness to support older kernels like DD-WRT does.