Not in 27" range, but in the price zone you're aiming for: TCL S400 series which has amazing input lag (almost nonexistent), HDR, and full 4k support, as well as being a nice Roku TV.
27" is so... small. For under 500 you could get a 55" that will be a much better viewing experience if you plan to sit back and enjoy rather than sitting with your face six inches from the screen.
Here is the cheapest 4k tv on the market:
TCL 55S405 55-Inch 4K Ultra HD Roku Smart LED TV (2017 Model) https://www.amazon.com/dp/B01MTGM5I9/ref=cm_sw_r_cp_apa_ncDoBb7K8J1BD
And if you're skeptical here's the LTT review: