You must dump your own legitimate Switch game cartridges (using a modded Switch) to create ROMs. Downloading Switch ROMs from websites is piracy and illegal in most jurisdictions.

: The best way is on the Nintendo Switch . This gives you access to the official servers to share and download millions of community levels.

If you specifically want a "download," there are standalone Android apps (APKs) that act as level creators, though they won't run within the PPSSPP emulator itself. How to Set Up Super Mario Maker Fan Game on PPSSPP

The game relies on Switch-specific features like the capacitive touchscreen for level building and modern networking for the "Course World," which a PSP emulator cannot replicate. Legit Alternatives for Different Devices