VLC as always saves the day. Most recently for me when you want to watch HDR UHD ripped to 1080p. With plex, this becomes a problem you need to buy a plex pass for and more significantly, must have a '16 Intel CPU or newer to be able to remap it while VLC does so in the fly.
Details: In plex, the colors are so washed out it looks like a black and white movie. In VLC, the colors hit you like
Addition: I tried two remedies while packing with handbrake. BT.709 colorspace and a custom one from reddit. Both lead to the movie being so dark that you cant see most of the details.
Conclusion: VLC being open source, we should be able to see what they are doing and copy this behavior. if plex wont do it without payment, this could be huge for jellyfin for example.
Anyone with actual knowledge who can shed light on this?
It sounds like you are having trouble with tonemapping HDR to SDR on the fly. This is a non-trivial task, but not impossible. Both mpv and ffmpeg (which plex and jellyfin use) are capable of this. If you install mpv, it will by default do the tonemapping, you can enable/disable this or force use of a particular algorithm if you like.
To answer your question: Plex has been pretty shitty for years now, and it’s only getting worse. They just don’t care for their user base.
ETA: Jellyfin also already does what you want, I think?