To make WiiM Mini compatible with Netgear Nighthawk mesh network, please assign different names for your 2.4 Ghz and 5 Ghz. Then you can connect WiiM Mini to the 5 GHz network. When you're using it, please connect your mobile device to this 5 Ghz wireless network too. 

Here are the detailed steps:

1. Launch a web browser from a computer or mobile device that is connected to your mesh network.
2. Enter http://www.routerlogin.net.
3. Enter the router admin user name and password.
4. Select Customize WiFi Network.
5. Select the Customize 2.4 GHz WiFi Network or Customize 5 GHz WiFi Network check box.
You can add a WiFi network in the 2.4 GHz band and the 5 GHz band.
6. To control the SSID broadcast, select or clear the Enable SSID Broadcast check box.
7. To add an SSID, type a name in the Customized 2.4 GHz WiFi Network Name (SSID) or Customized 5 GHz WiFi Network Name (SSID) field. The default SSIDs are NETGEAR_2G and NETGEAR_5G. 
8. Set the WiFi security
9. Set a WiFi password in the Password (Network Key) field.
10. Click the Apply button.
Your settings are saved.