What?

NXP's i.MX 7 was released in 2013 with Cortex-A7 + Cortex-M4 and well supported back then. And there probably were earlier chips.

Yeah Linux is slow at developing features for embedded systems. That's why embedded programmers run code outside of Linux. Fortunately, Linux has kernel modules to make it easy to do things like that.

Historically, Linux isn't even a proper embedded OS. Linux continues to get better-and-better for embedded but I'd expect that 2013-era was dominated by VxWorks or other embedded OSes with a better featureset for embedded. It was _LINUX_ that was the problem in my experience, at least back then.

But then WindRiver (makers of VxWorks) added a bunch of features to the Linux kernel and now today Linux is acceptable for embedded. I dunno exactly when the switchover from majority VxWorks embedded systems -> WindRiver Linux -> and now each manufacturer has their own BSP / Linux support... but a lot of what you're complaining about was software development.

Even then, a ton of older embedded crap ran their own custom versions of Linux 2.4 or whatever and just maintained a separate branch. I'm guessing these older embedded systems got their start in the early 00s and just had issues upgrading past the Linux 2.4 -> Linux 2.6 jump.

Or in other words: it was far more likely that Linux wouldn't support Chip X, rather than Chip X was unable to support Linux. Or maybe a chip did support Linux but most of the codebase was stuck on Linux 2.4. Or if Linux support existed, it was effectively proprietary custom kernel modules that individual teams wrote for themselves rather than a community-driven internet-based workflow. Etc. etc. Linux was harder back then.

But the stuff you're talking about is early 2010s, if not 00s. Damn well over a decade, might be closer to TWO decades (and the only reason I don't know that is because I was a wee-little ignorant student back then and don't really know things older than 2010s....)