https://www.polygon.com/2017/10/8/16444084/snes-classic-hacked

The SNES Classic hack attempts began the moment the console was released, and it appears as though it’s now possible to add your own ROMs to the system.

The above video gives you a detailed rundown of everything you need to do if you’d like to add a copy of ActRaiser — or whatever other game you’re missing — to the system, but be warned: This isn’t a simple process. You also run the risk of bricking your console, and it’s not like you’re going to be able to just buy a new one if that happens.