It works for most people but there’s some issues with some monitors where the color saturation doesn’t work well and result in washed out colors compared to SDR.
It will also output RGB into YUV buffers if you have a display that only supports YUV colorspaces, so you end up with a very green and reddish purpleish screen.
Initial HDR support was introduced in 6.0, and 6.1 is supposed to bring some fixes for the washed up colors. I haven’t found a bug for the YUV stuff and didn’t have time to do a proper bug report.