This is a list of alternate ways to install custom firmware, intended to be used when your 3DS is for some reason incompatible with the guide's instructions. If you're getting assistance with installing custom firmware, you will probably be linked to a specific subpage based on your scenario and the additional hardware that you have (if applicable). Otherwise, if you know what you're doing, feel free to follow these guides if you're curious.
Non-Seedminer methods
System Version 1.0.0 - 11.15.0 with Freakyforms Deluxe
/Installing boot9strap (freakyhax)
System Version 2.1.0:
/Installing boot9strap (2xrsa)
System Version 4.X.X or 6.X.X with a DS flashcard
System Version 9.0.0 - 11.9.0 with Cubic Ninja
Seedminer-based methods
You will need to follow the Seedminer page before proceeding with the following. You will also need to update to system version 11.16.0.
Steel Diver: Sub Wars
/Installing boot9strap (steelhax)
Pokemon Picross
Methods no longer usable
These methods are no longer working and are for preservation purposes. Please follow any other method instead.
/Installing boot9strap (safecerthax)