I do this. It's the best. You can buy used HP or Dell mini workstations on eBay for super cheap.
Full Linux, full ad blocking, full access to every streaming service instead of just whoever makes an app for your particular TV.
And with the enshittification of smart TVs injecting ads everywhere they can, keeping it disconnected is the only way to fly. Modern tech is like Skynet, you can't let it connect or it's the end of the world.
That doesn't make sense, a "browser spoofing" addon most certainly doesn't do anything that would be detectable by an ISP listening in on an encrypted connection.
Amazon is not an ISP though...? In this scenario, Amazon Prime Video is a server that is receiving a series of HTTP requests. User agent spoofing absolutely would work in that scenario.
That is why I'm not subscribed to any of them. If they don't want to offer me the same bare minimum, it's on them. I mean why are they even doing that? To protect against piracy? Yeah, that seems to be doing absolutely nothing then.
This is the point where you download qbittorrent on the machine, and hop on your favorite torrent site to go get whatever show or movie you want for free, and play it on VLC. Just make sure to use a VPN if you live in a country that enforces piracy law. My reccomendation is Mullvad VPN ($5/month) if you care about privacy, and literally whatever's the cheapest if you don't.
Some cheaper brands, which are subsidized via ads, actively search for unsecured networks. Disabling the Wi-Fi as completely as possible might be worth the time, if you have such a model.
I don't even think it's limited to the cheaper brands. I thought I heard about Samsung (or some other similarly large vendor) TVs connecting to networks their servers knew about for updates and stuff all of course without your interaction/consent. I might have just read that as a possible future thing though it was a while back that I saw it.
If you're ready to put it into action, you might want a network attached storage device (NAS) to run your *-arr stack and store your stuff. I recommend a Synology NAS with at least 4 drive bays and a redundant drive.
You should do all of this behind a VPN. I recommend Proton.
My rig is set up to run in containers with docker-compose. I automated it all to the point that I just have to boot up my NAS and the torrenting starts up automatically. It's all managed through websites hosted in various containers on the NAS that I can access from any other device on my network. You can read the docker docs here: https://docs.docker.com/compose/
Also, it's a good idea to run pi-hole for a network-wide tracker-blocker and ad-blocker. You should have your pi-hole devices on your network as a separate device that doesn't do anything else. I have 2 pi-hole devices on my network. The hardware they run on is just the smallest Raspberry Pi's I could find at the time. I connected them to the network via WiFi and plugged them in behind a dresser in one bedroom and next to the wifi router in the other room.