Hi thank you for the information.
I actually found the solution to my problem here:
https://github.com/linuxserver/docker-mods/tree/jellyfin-opencl-intel
The docker creator added a mod to the provided docker app that enables tonemapping. You just have to add a new environment variable as stated on the mod page to the docker configuration.
Variable „DOCKER_MODS“
Value „linuxserver/mods:jellyfin-opencl-intel“
This only works using the „Linuxserver“-Docker App:
https://github.com/linuxserver/docker-jellyfin
It can be installed from the Unraid App Store.