Following instructions are provided without any warranty, and may even get you in trouble legally. The instructions are provided for testing, learning, preventing e-waste, and should be use with care. We (including contributers + commentators) are not responsible for any damage to your device(s) or any legal issues.
Instructions have been moved to https://github.com/francoism90/asus-router. :)
hmmm :-/ weird... I had once an issue, that U-NII-4 channels were not selectable ("were not there") because I did not set them in NVRAM via init-script.
What kind of router model do you have AX88U or new one AX88U PRO?