Interesting observation, and something I hadn't really though about. For my own stuff I increasingly pick older technologies, not really retro, like jcs does here. Personally I think I've just grown tired of the modern "stuff", it's way to complex for me to find it relaxing to write a few lines of code for the fun of it. I wonder if that's true in a boarder sense for others working in IT.
I've watched a few of these videos, where jcs just hacks away on his old Mac and I'm extremely impressed with what's actually possible on these old machine. I do think the compile times would drive me insane, but others might see it as a nice little break.
I think there are far better retro hardware choices to relive writing native programs for. Stuff you'll actually be able to ensure will run successfully with full graphics and sound capabilities on every instance of the thing. C64, Amiga, etc. There's a reason the x86 PC severely lagged behind in the demoscene for ages, it was just miserable hardware to support.
Granted, I'm using it on homemade game engines, which are very amenable to the simple type of code C allows you to write. I wouldn't want to write an HTTP server in it. But for what I build, I find using C to be the equivalent of woodworking, compared to the Ikea furniture I put together at work.
Some of them have been programming it before it was even proper silicon, when it was being developed via FPGA. Lots of really in-the-weeds discussions on machine code and cycle timings and such. Worth diving in if you like seeing "how the sausage is made."
One of the current projects is implementing a sega genesis/megadrive console, using the different cores to emulate different components: https://forums.parallax.com/discussion/173381/console-emulat...
Offers will vary, but, if impromptu answers carry any weight, then off the top of my Sunday afternoon head, this is the first reference that percolates to the surface.