I have a previously cfw 2ds (I unhacked to sell but no-one want) and want to do seedminer but it got banned before I unhacked so can anyone advise me on what to do. If it helps my bro has a cfw 3ds on an older version. I currently don't have them with me but will soon
You could try Frogminer if the system already has a copy of Steel Diver: Sub Wars (not the original Steel Diver) installed. Search for the Frogminer topic in the Flashcards & Custom Firmwares forum.
You could also buy a flash cart and use the ntrboot method which is a lot easier but will cost you about $20 or so.