Here is my Teensy 4.1 on a breadboard pretending to be a Commodore 64. USB keyboard, color text, background, border, and D64 (1541 image) support for LOAD/$/SAVE. 6502 emulation supports machine language, and Commodore 2.0 BASIC programs. Sorry text only, no games, no graphics, no sound, no joysticks, just simple stuff for now. But that simple stuff works! (mileage may vary, lightly tested, please try this at home under controlled conditions).
My Open source: https://github.com/davervw/c-simple-emu6502-cbm/tree/teensy_lcd
Also see link from Adafruit's blog!