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. :)
Something like this (adjust channel and other things you need)
settings for 5G
wl -i eth7 down
wl -i eth7 regulatory 1
wl -i eth7 spect 0
wl -i eth7 chanspec 100/160
wl -i eth7 up