Then go to the GL-AR300M router using HTTP the browser 192.168.2.1 In the router menu Network => Interfaces => LAN change the ip address so that it does not match the ip address of NanoPi R2S ?
It is called a bridged AP. https://openwrt.org/docs/guide-user/network/wifi/wifiextenders/bridgedap
The IP address of the AP should be in the same network (192.168.1.X/24) as the main router but a different value of the last byte than the main router. For example leaving the NanoPi LAN at its default of 192.168.1.1, use 192.168.1.2 for the AR300M.
Thank you for your answer. I will try it soon. Why do you think the option I suggested is not optimal? The IP address can be changed in the settings, for example, change 192.168.1.1 to 192.168.100.1 ..
If you connect wan to the upstream LAN, the GL will be unnecessarily NATing the wifi users. If everything is bridged into the same LAN there is only one stage of NAT and routing, which happens in the main router with its much faster CPU.