I came here to advocate much the same.

Raspberry Pi Zero + Risc OS Pico.

The fastest BASIC interpreter ever written, with local variables, recursion, inline ARM assembler, and more.

Advantages over Python etc. on Linux:

* No complex OS underneath;

* No need to learn arcane concepts like "editors" and "files" yet;

* No significant whitespace;

* No weird C-isms like the output statements, the two meanings of % or any of that legacy nonsense it inherits from 40y of crap underneath;

* Zero maintenance required.

Blinding fast, cheap as chips, runs on a dribble of power, solid-state and silent.

If the kid takes to it, can be trivially enhanced to a full rich GUI OS with tons of educational apps and software.