Thanks for the help, but I'm not running Jellyfin in a container, but on a qpgk. If I still can make it to host networking mode, I'm not sure how would I do it.
I cannot see it, sadly. And I don't know enough about how my NAS runs to actually search about that config, since I've always used it with official apps until now. I'm sorry I cannot give more info, since I'm the one asking for help.
Oh, yes, that would be Container Station (tried that when trying to set remote access via Caddy and nginx), but right now there is no container active there, since Jellyfin is installed as an app. I've just checked just in case, and there is no containers (only both unused images for caddy and nginx).