This article explains how to turn off HDR on a Roku TV. These instructions apply to all Roku TVs that support HDR.
HOW TO TURN OFF HDR ON A ROKU TV – Watch HDR Content During the Day
To turn off HDR on a Roku TV, use the Roku remote to open the secret menu:
On your Roku remote, press the Home button five times, then press Rewind, Down, Fast Forward, Down, Rewind.
Select Change HDR Mode.