If your country is not listed on the TP-Link website, you can still update your firmware by downloading it from the global site or from a region that matches the hardware version of your device. The most important thing is that the hardware version (for example V1) of the firmware file must match the hardware version printed on the label of your router. The firmware is not locked to a specific country but to the hardware version, so you do not need to worry if your region is missing For your second question yes you can use Ethernet backhaul with EasyMesh. If all three models support EasyMesh (Archer BE230, AX53 and AX55 Pro do), they can form a mesh network and Ethernet can be used as the backhaul link between them which is usually the most stable and fastest option