Oh snap SHARP owner here with the same problem, this with my other ongoing audio issues is sooo brutal. Thought is was maybe a Sony PS4 firmware thing as I don't get to play often, but it happened it on two different android boxes that were working perfectly fine, so that's out question. I don't know what's would have been worst if it was a hardware issue. Un-mounting it, unplugging dozens of cords, packing it up and having to driving to Fed-Ex and praying Hisense QC is up snuff to replace the ports correctly without damaging something else. Or hoping that Roku can actually properly fix a software problem in some timely manner when it's been over 2 years for the multi-audio-surround sound issue. It's like choosing between getting hit in the eye-socket or a kick to the groin. I'm reluctant to even post this but I found a couple of temporary fixes, as I feel like it will give "them" more incentive not to do anything, but why should other people suffer. I have a Sharp LC-65Q73+ TV on Build 9.1 by way, so it's not TCL consumers getting the shaft. All built in apps and USB port don't have any issue with HDR.
1.Hitting the home button/main menu on the remote and then going back to the source/device.
2.Turning the TV on/off, just make sure you turn CEC or whatever it's called off on both the TV and device as this just put my PS4 to stand-by. Also Disable Fast TV start
3. Unplugging the HDMI plug and quickly plugging it back.
The HDR logo should pop-back up and if you press enter on the remote it's should show whatever resolution your in and HDR10. The only thing that sucks about this if you going go to the Dashboard on the PS4 or some title screen/file explorer that SDR you have to do one of these again or it super DARK again.
Tanner or if some other community manager is reading this I already did all the trouble shooting while trying to fix my other audio issue, used 7 different HDMI cables, moving to different ports, System restart, and a factory reset. Made sure HDR was set to Normal or High none of it worked, fiddled with HDMI setting. Just fire up COD or Red Dead Redemption 2 or any HDR game and after the initial loading screen and the "switch" happens you should be able to see or actually not see what we are talking about. I can not type out how disappointed I am with this company as ever patch just makes something worst and I'm a very patient man. Please fix this ASAP or better yet acknowledge the problem!