While the porting of NETBSD used to be a meme, these days there are far more embedded platforms supported by Linux in some fashion.
Sadly not all on the mainline, but having worked in the embedded world, Linux is a massive part of that space.
I think it's reasonable to eventually treat 32-bit embedded in the same manner we treat 8-bit and 16-bit embedded today: as "weird" architectures that have their own bespoke OSes (even if it's a fork of Linux or BSD), and on which "normal" portable code is not really expected to compile or run without modifications.