What are the specs of the server? It looks like it is extracting the subs, dumping the attachments, then remuxing. So, other than disk space, it should be a pretty light load on the server.
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