How to make your own DOS-on-a-Stick: 1. Install @micropython or @circuitpython on your dev board, 2. Copy PyDOS files from https://github.com/RetiredWizard/PyDOS to your board using e.g. Thonny, mpremote or rshell, 3. Open the #Micropython / #Circuitpython REPL and do a soft reset by Ctrl-D. PyDOS should load automatically. You can add your own autoexec.bat or edit menu.txt.
GitHub - RetiredWizard/PyDOS: DOS-like OS for microcontroller boards running Micropython or Circuitpython
DOS-like OS for microcontroller boards running Micropython or Circuitpython - RetiredWizard/PyDOS