We simply use an open-source alternative chip that replace the CIC chip. The most common one is the SuperCIC (https://sd2snes.de/blog/cool-stuff/supercic) that you can flash onto a wide variety of chips (depending on your PCB). This is the chip that is used in the SD2SNES / FXPAK flashcart.
For this particular release, we simply used Infinite NES lives's Multi-Region CIC (http://www.infiniteneslives.com/snessupplies.php), that works very well too! They will be already installed on a blank SNES cart if you buy them from Infinite NES Lives, but you can also buy the chips separately like we did to mount them on your own PCB if you choose to go that route :) .