Running at 200Mhz rather than 4GHz though is hard to accept for most people, even though retro OSes make the experience quite smooth overall.

I’d argue stuff like the various bootrom exploits for Apple SoCs and similar, used for jailbreaking, is the other side of this. And that one gets you open computing at a much higher perf, although not necessarily malleable, and is not going to be a long term viable strategy.