– Installing firmware for a different R4 clone will make the card stop working (black screen, "Loading..." stuck, or "Menu?" error).
Many 2014+ R4 cards include a "time bomb" that causes them to stop working after a certain date. You can bypass this by: r4 sdhc 2015 dual core firmware
However, because these cards were often clone cards (unofficial reproductions of original R4 tech), you cannot use just any R4 firmware. If you try to load the official R4 Wood firmware or the firmware for an R4i Gold 3DS, your card will likely brick or fail to load. You need the specific kernel designed for this specific year and model. – Installing firmware for a different R4 clone