Unfortunately this time it is not so, I tried all the channels, the AC mode does not want to work.AFAIK you don't need to do anything special to activate it AC on your network card, there are options you can configure. I just switched on my wireless network card and disabled my ethernet connection and I am able to connect to my AC wireless network without needing to configure anything extra on my wireless network card. If you want to use AC I would enable AC on your wireless router and play around with the different "Wireless Channels", just try all channels until starting from the top and then moving down until you find one that works.
it is still very strange because I have the latest stable firmware openwrt OpenWrt 21.02.0 r16279-5cc0535800 / LuCI openwrt-21.02 branch git-21.231.26241-422c175.
I don't understand why only this network card doesn't want to work in AC mode