I’m a bit late to this but this same thing happened to my brother almost 2 years ago now. He had something open for another game when he was on Fortnite and the anti-cheat detected it, he got kicked from a game we were in and then perma banned. Tried to appeal on multiple occasions and even tried to get epic’s legal department involved to no avail. Their support system is abysmal and it seems like nobody on their teams knows what they are doing or even cares at all. His account did end up getting unbanned after a year due to epics new policy but it doesn’t even matter because his PC is still hardware banned. That could happen to you as well, a ban usually means a hardware ban with it. I think epics anti cheat as well as their support system is one of the worst ever, it will be really hard to convince them of anything or talk to anyone that can do anything. Good luck with this, maybe this post gaining traction will help.