To connect your box via Ethernet, simply connect the Ethernet cable from your hub into your Sky Q box and wait a couple of minutes for your box to automatically connect.
If you don't have an Ethernet cable, you can buy one through the Sky Shop.
Disable 2.4GHz and 5GHz wireless
Once you've connected your Sky Q box to your hub via an Ethernet cable, you'll need to disabled 2.4GHz and 5GHz wireless:
Reference: https://www.sky.com/help/diagnostics/setting-up-sky-q/connect-to-sky-hub
Other Reference: https://www.expertreviews.co.uk/tvs-entertainment/pvrs/1404726/how-to-fix-sky-q-connectivity-problems/page/0/4