To install Luma Updater 2.6 using a QR code, you will need the homebrew app already installed on your 3DS. Launch FBI from your 3DS Home Menu. Select Remote Install from the main menu. Select Scan QR Code . Point your 3DS camera at the QR code below:
I can give you the exact manual steps to fix it if the QR code method fails. Releases · KunoichiZ/lumaupdate - GitHub luma updater 2.6 qr code
Ensure your 3DS is on the latest official firmware before updating CFW to ensure everything remains "Safe to Update". If the updater fails, you can always manually copy the new to the root of your SD card. To install Luma Updater 2
Download the latest boot.firm from the official Luma3DS GitHub and replace the one on the root of your SD card. Select Scan QR Code