Archer C7 v5, I did:
uci set wireless.default_radio0.ieee80211v=1 uci set wireless.default_radio0.ieee80211k=1 uci set wireless.default_radio0.bss_transition=1 uci set wireless.default_radio1.ieee80211v=1 uci set wireless.default_radio1.ieee80211k=1 uci set wireless.default_radio1.bss_transition=1 uci commit reboot
I have 802.11r turned on for both bands, same SSID and key etc. My Galaxy S9 which supports these protocols, doesnt go to 5GHz from 2.4GHz when the signal is excellent. Is there any other config that Im not aware of?