Is there a list anywhere of which subtitle formats each client can direct play? The documentation seems to only mention which sub formats each container format supports.
I think it is an overlap between what the client supports and what the device/OS supports. On one of my Android TV devices it transcodes with ASS subs (CCwGTV 4K). On another it direct plays (Sony Bravia UR3 4K). Though it struggles with the fancier Anime OP/ED ASS subs.
So having a definitive compatibility list is difficult.
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)