How is Jellyfin installed? What OS is the server running. Can you share one of the ffmpeg log that jellyfin generates? You shouldn't need to change the ffmpeg path.
Jellyfin 10.10.7 (Docker)
Ubuntu 24.04.2 LTS w/HWE
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
4x WD Red Pro 6TB CMR in RAIDZ1