KrzysioCart MicroSD is a new flashcart for NES/Famicom. It currently supports 81% of NES library, and is under development. An extended version, which will support save states, Game Genie codes and expansion chip support, is planned. https://forums.nesdev.com/viewtopic.php?f=9&t=15757

Yeah krzy is pretty impressive, he can also produce one off carts if you have games with atrocious mappers like Taiwanese/Russian bootlegs which are currently not supported, my guess is something to do with storage. The 81.5% he mentions is quite reasonable for most consumers and it's far far cheaper than the alternatives.