[jarcane]

For the Raspberry Pi, there is Risc OS Pico, a barebones Risc OS image that boots directly to BBC Basic. https://www.riscosopen.org/content/sales/risc-os-pico

There's also the FUZE and FUZE BASIC, a retro-y keyboard case and BASIC dialect for the Pi. https://www.fuze.co.uk/

I would also second the suggestion of the PICO-8, which is a Lua-based retro virtual console complete with its own built-in dev environment. http://www.lexaloffle.com/pico-8.php