Review on ASUS PG329Q: 2560X1440P DisplayPort DisplayHDR, 175Hz Refresh Rate, Flicker-Free & Adjustable - A Comprehensive Review by James Manning

We understand that most modern PC monitors don't have true HDR. But if you want to make a monitor with HDR capability, you need to make sure it works. HDR does not work on this monitor. ASUS has confirmed that the PG329Q has a built-in feature that dims the brightness after HDR has been enabled for an hour. You can turn it on manually and it will run for about an hour, but then dim again. You don't have to take my word for it, do a quick google search and see how many people are having the exact same issue. Otherwise it's a pretty good monitor but I'll keep looking.