sounds like your server is transcoding and converting to 1080 (losing the hdr).
I don’t know if your tv can stream 4k with plex, you might search the forum with your specific model number.
for general 4k info see @ Plex, 4k, transcoding, and you
for smart tvs in general
- almost all of them have 100mb ethernet, which is not fast enough for many 4k movies
- none of them support HD audio (ie truehd+atmos)
- a lot of them have limited subtitle support
- if the audio is transcoding+subtitles enabled = this will cause video transcoding
