Buy a cheap smart TV and run it in "store mode".
Brightness and saturation will probably be maxed out but with a cheap TV, it looks more like "normal" on a more expensive model. Hint: The main difference between cheap and expensive in some cases --- the color adjustment range is limited by software on the cheaper models.
Currently using a Hisense 4k model from Costco connected to a small mini PC --- Windows or Linux, your preference. The TV functions as nothing but a dumb display.
Use a small "air mouse" for control. On screen keyboard as needed.
Use a Hauppauge USB tuner for local digital broadcasts.
I use software called DVB Viewer to view local channels and IPTV. A browser with VPN for streaming in some cases.
In every case, I maintain full control of my data and the ability to block ads as I see fit.