I'm imagining something like a "software choice" act which requires all network connected devices to be able to, in principle, have their bootloader unlocked an

I'm imagining something like a "software choice" act which requires all network connected devices to be able to, in principle, have their bootloader unlocked and an alternative operating system loaded in with relative ease. No specialized tools, you can't say "well just unsolder this chip" but you can display a prominent warning that the bootloader is unlocked. Basically do it like android does it, but by law. There are obviously some specifics there, like if the camera on my phone has a firmware blob, does that need to be able to have the firmware updated? A lot of little caveats like that make such a law difficult, but I think with hardware access the open source community can flourish on devices like smart TVs, etc.