I have a 2020 Frame 65" so the menus may not be exactly the same, but here are some things I did (in the order I did them) to bring up the brightness for HDR content on Disney+ and Prime. I'm using the built-in streaming apps and I'm not aware of any "disable HDR" setting on my TV.
With these settings, movies look really good at night, and are good enough in the daytime:
1. Make sure that any light sensors for Intelligent Mode and Eco settings are off. 2. Have Brightness and Contrast at the highest settings. (These were the default settings for my TV.) 3. Turn Contrast Enhancer to "High". 4. Increase the gamma slider for the selected curve to brighten the screen without washing it out too much.
You don't have to use all 4 steps, sometimes #1 and #2 are enough depending upon the movie. The Mandalorian is unwatchable without #1/2/3 anytime and a little of #4 in the daytime. Dr. Strange is another really dark movie. Both Guardians of the Galaxy movies are fine with #1 and #2 at night but benefit from #3 in the daytime.