My partner and I were gratefully surprised when we bought a cheap Hisense for their cozy space (to isolate when overstimulated and just play some games) that in the setup it offers the option for a ‘dumb TV’ mode with no requirement for internet. In addition you can reject the user agreements and still use the TV. It boots straight to HDMI, no pop up ads, and is snappy.
For a TV that can be set up as a ‘dumb tv’ and you can even reject the terms and conditions: Hisense surprisingly.
My partner got one a month ago and it was stupid simple to set up and asks you if you want to set up as a Smart TV or as a Basic TV.
Also ditch the Roku, that’s absolutely just as bad as using the onboard smart tv functions. Theres NVidia Shield, Apple TV, or with a little setup a Raspberry Pi running Kodi.