Yep. Transcoding looks just fine. The Windows client has a log in C:\Users\your user\AppData\Local\JellyfinMediaPlayer\logs. Maybe there is something in there that will help us figure this out.
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)