Ok, people don’t know how networks work. Frequencies, 2.4 or 5 ghz has no bearing on connectivity to a node. The number of routers you have doesn’t have any bearing on connectivity. I have 4 mesh network routers that use both wired and their 6e proprietary backhaul with no connection issues. I also have 5 switches connected to these mesh routers and in the wiring closet with no issues. If you don’t know networks, you shouldn’t offer advice, it’s going to confuse the OP.
I mentioned in another thread on this that you have to setup the streamer with the correct network settings, which includes static ip or dhcp, and subnet mask. Can you ping the streamer? Can you look at the router device list to see if the streamer is attached to your LAN? Concentrate on getting the streamer connected hardwired to your network. Then go from a wired pc to your network and ping the streamer. If that doesn’t work, your streamer isn’t configured correctly. If the wired method works, then concentrate on your wireless connections. Your router will tell you if both your tablet and streamer are connected. This isn’t that tough to do.
Im assuming you are using Roon and if so, didn’t you have Roon ARC turned on? If you didn’t you should. You can get rid of Sirius/XM in your cars but you will have to make changes to your router to use port forwarding.