I reported this issue back in the summer to the devs, said they are aware and maybe will fix, just reboot the phone if hdr is not being played or only being played in certain scenarios. I didn’t find any fix for this in any patch.
So I check HDR content on youtube, it turns out it’s still broken. It only turns into HDR if I tap the screen or hold my finger on the screen. If I lift my finger, it goes back to SDR. And it’s clear as day it’s broken.
Do you have this issue as well? Just want to make sure it’s not isolated to my device. And no, rebooting my phone does not and never did fix this issue.