This will work on any current 3DS / 2DS, including the recently released New 2DS.

Your gonna need an old DSi flash card, the favorite being an AceKard2i or one of its clones.

more info here : https://gbatemp.net/threads/ntrboot-released.472585/

It's not very noob friendly, so be warned it will need a fair bit of researching if you wanna do it.