I know very little about ipv6, but CGNAT is Carrier Grade Network Address Translation.
NAT (Network Address Translation) is how your home router takes your one public IP address and is able to simultaneously allow your phone, your PlayStation, and your smart fridge use the internet.
CGNAT is basically the same thing expect on a much larger scale and controlled by you ISP.
KDE bigscreen looks perfect for me. I know I have heard of it before but I will need to look a bit more in depth at it.
All I want is Roku, but FOSS, without the ads and tracking.