The Subtitle Extract plugin runs on a schedule. You can go to the dashboard and run it manually. Depending on how big your library is it might take some time.
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