Which IPV6 address are you using when connecting from outside? Your router's IPV6 address or the server's IPV6 address. You should be using your server's IPV6 address.
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)