To be noticed that
- Unplugging Camera FFC makes the console work, but you cannot format it (otherwise it will be stuck at 3D Face Raider's confirmation or something more serious) or enter the System Settings with Luma3DS Exception Handler enabled.
- I don't know about Old3DS(XL) much, but I can confirm that a New3DS(XL) cannot be booted with either Upper Screen FFC or 3D FFC unplugged.
Anyway, congratulations to OP's console to be temporary fixed.
- Unplugging Camera FFC makes the console work, but you cannot format it (otherwise it will be stuck at 3D Face Raider's confirmation or something more serious) or enter the System Settings with Luma3DS Exception Handler enabled.
- I don't know about Old3DS(XL) much, but I can confirm that a New3DS(XL) cannot be booted with either Upper Screen FFC or 3D FFC unplugged.
Anyway, congratulations to OP's console to be temporary fixed.