Emby and Jellyfin run on the same port (Jellyfin is forked from Emby). Did you actually succeed in starting Jellyfin? You can't run both at the same time without changing what port one of them runs on.
Jellyfin 10.10.3 (Docker)
Ubuntu 24.04 LTS
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
3x WD Red Pro 6TB CMR in RAIDZ1 (JF Library)