I know two solutions, both not ideal - ironcast.tv seems to promise that initially, but on the one side it is unclear how much vaporware the thing is, on the other side, it will still be based on top of Android and needs to be on the WiFi. - Buying Commercial Digital Signage Panels. I found it impossible to find reviews on the internet. It is unclear for me which panels are actually good for watching movies.
Option 2: Buy a projector. The home theater models are scrutinized closely by reviewers for video quality and, last time I checked, come without smart TV features. Prices range from merely expensive to blisteringly, eye-wateringly expensive but can be ameliorated slightly by purchasing used units.