I misread the original post -- now I see that you are connecting the streamer by WiFi.
Yes, as others have said, the modem needs to be in pass-through (modem only) mode. That means its WiFi will be off. I believe most Netgear stuff has a sticker on the bottom with its default IP address, user name, and password. You can contact the modem then from a Web browser on your network and check & change settings.
If you can run a cable from the streamer to the modem, why not run the cable from the streamer to the router instead? Most of them have 4-8 Ethernet ports in the back. (I just checked; yours has four.) If not enough ports, a $20 unmanaged switch will help.
Routers I’ve used consider wired and WiFi devices all to be on the same network by default. They draw IP addresses from a common pool. What I’m trying to say is, they can talk to one another.
(BTW, Category 8 cable is absolutely unnecessary at those speeds. Cat 5e is plenty, though there is nothing wrong with Cat 6 or Cat 7. My understanding is that Cat 8 is shielded and the shield grounding is said to reduce isolation between devices. Some very tweaky folks complain of higher noise floor, but I have no experience with that.)