Comment by pjmlp

You can start here, https://wiki.osdev.org/Expanded_Main_Page

Also regardless of what others say, you can have a go trying to feel how it was to use BASIC in 8 bit computers to do everything their hardware exposed, or even 16 bit systems like MS-DOS, but with Python.

Get a ESP32 board, and have a go at it with MicroPython or CircuitPython,

https://docs.micropython.org/en/latest/esp32/quickref.html

https://learn.adafruit.com/circuitpython-with-esp32-quick-st...