PlayStation 2 can play homebrew games by using DVD player exploits – Engadget

You generally need to install a modchip, purchase a specially-configured memory card or even pry the system open to block the disc readers sensors. It might simply be a matter of using the discs themselves to fool the console.
You can even boot into a menu to choose from multiple video games saved on a single disc. That might not be an option for long when some PS5 designs will not include disc drives, however it does raise hope for those wanting to broaden their game collections with unofficial titles.