As long as the firmware is proprietary and cannot be inspected or modified, the only reliable way to avoid snooping by tech industry is not to connect any "smart" device to the Internet. Use the TV as a dumb monitor for a PC under your control (running Linux). If streaming service X will not run on Linux because DRM is not implemented or enforceable on a free device, do without it, or find alternative sources for the content (hint: Linux ISOs).
You say "only", but if it is illegal, optional, and can be detected freely, it is very likely to not happen. For all the snark one can muster about DOJ, with those three things in place, it could get expensive very quickly to try to circumvent the law.
I've been using my pi-hole as my DNS and then also firewall blocking the TV from phoning out on port 53 in case the manufacturer has hardcoded DNS. Though I agree with the point and I shouldn't have to do this. This is just mitigation.