Yeah, this is the frustrating part. I've worked with retailers on in-store displays, so I know that you can get high-quality, cheap panels that are "dumb" in that they don't have apps, but they do have full local-only operating systems that can access wifi networks and list files. Some of them can even boot into a chrome-based kiosk mode, indicating a full html rendering stack.
But if you check for anything DIY, they're either sourcing panels directly from manufacturers in China, or ripping apart smart TVs (or just "not using" parts of them). There's a happy middle ground and I know, from experience, that's it's not an expensive one, even though I also know from experience that it's often times an extremely pricey one. By which I mean, the panels themselves are cheap for an outlet to get and use, while actually trying to buy a panel from those outlets is reserved for B2B applications and is priced for enterprise work.
What I was hoping for is that someone who knows about those kinds of panels and that kind of work would be able to say "Ah, yeah, here's a great panel that we use for our displays which is a good deal".
But, so far, I've never had any takers on that. It's a small industry (or, at least it was when I was involved), so that's not unexpected. But I keep hoping that some dogged youtuber or some experimental blogger will figure out how to source all the bits for the TV that so many of us want, but that there's is strong business disincentives to create.
That's what's most galling, I think. Samsung/LG/Sony could make this and sell it, but they refuse to because it would provide an alternative to the market they really want which is ad capture/data harvesting. And I'm just so tired of that being the only option for that specific reason. Because now I'm stuck here hoping that someone out there makes the least-complex, cheapest, and fastest thing for a TV manufacturer to make, which seems like the dumbest thing to have to hope for.