Earlier quoted context omitted.
The Raspberry Pi 400 is basically this. https://www.raspberrypi.org/products/raspberry-pi-400/
The 400 isn’t quite what I had in mind. I was thinking more of a device usable even by the under-10 group, with a simpler and more robust physical design and, crucially, the kind of instant-on, guided programming environment the early home “PCs” had. With early Sinclair systems, each key on the keyboard would act like modern auto-complete: you would start typing and keywords would appear almost magically. On the BBC…
OTH... Taking a RPI400, and build a stripped-down linux system which resembles Sinclair BASIC could prove to be a fun exercise.
Edit: I just realized how expensive the ZX81 was here in Germany back in 1981 - it'd set you back 450€ by todays value.