there exist flash carts where you can insert SD cards and load them on your gameboy at least the guy who wrote https://news.ycombinator.com/item?id=26857743 ht

there exist flash carts where you can insert SD cards and load them on your gameboy at least the guy who wrote https://news.ycombinator.com/item?id=26857743 https://news.ycombinator.com/item?id=26857743 has custom cartridges for his games