M1 devices actually have quite an interesting boot security model, so you can install a custom kernel and OS and boot it, without compromising the security of the platform for normal users that have never heard of an operating system.

While a dev board would be cool, a Mac mini with the hardware UART enabled over a USB C cable is getting pretty close!

Trade offs like these arguably could help to keep general purpose computing alive, as they show it is possible to deliver a secure device to customers that can be used however you like, running whatever software you like, without iOS style "no choice available".

M1 laptops are general purpose computers already. You can also install an open OS.

Dev boards aren't necessary when an entire functioning laptop only costs $999. An M1 dev board be would way, way more expensive than that and far less functional.

Assuming this comment is from a "nerd", this illustrates exactly the point I am making. Trying to "convince or train lay people" to admire companies that allgegedly seek to control "basic access to computing". Apple computers are pre-built, they are not DIY PCs.

Note how the other replies to this comment besides mine refer not to the dystopian future predicted by the GP, but to the present.