I am running jellyfin in LAN on a Synology. I/O from harddisk shouldn’t be a problem being SSD on the same NAS. And WiFi should sustain a 4K stream. I have tried only web clients. How can I optimize the stream for such large file? Or how can I debug the bottleneck?
Not sure about Jellyfin but in Emby there are user settings to disable transcoding. They’re of the same lineage so maybe a good place to look.