Thanks @ybizeul ! Your changes did not stay on jsfiddle, but I was able to figure it out. I finally have internet again on my USG!
Have you experienced any issues with new devices getting assigned an IP when your TV is on? When the TV is on (when I say TV, I am referring to the décodeur TV), devices get a strange looking IP assigned to them. But when I turn off the TV, all the devices suddenly get assigned a correct IP. It seems the TV is interfering/blocking DHCP. Im no network expert, so I am not sure how to debug this. It may just be an issue with the config file file that I used from this thread (I force provisioned the USG using @jaydee99 config.gateway.json file).
The other issue might be how I am connecting the Livebox TV to my network. I know a direct connection from the USG WAN 2/LAN 2 port to the Livebox TV is the preferred method. But since my Livebox TV is quite far from where my USG is, I have to connect it through a switch. The image below shows how I am connecting it.
Let me know what you guys think. Thanks!