I'm not sure about the Swiftfin or the other Apple clients, but on the Android TV client there is a setting to passthrough Dolby audio. Does Swiftfin have something similar?
Jellyfin 10.9.11 (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)