Playback fails in browser on Android

[Aankhen]

I’m running Jellyfin on TrueNAS SCALE 23 (read: on Kubernetes) via TrueCharts. The system has a 48-core EPYC 7642 (that’s Zen 2, to be clear, from around 2019). I haven’t had any trouble playing things in Firefox from my Windows desktop or Linux laptop so far, but on my Android 12 phone, both Chrome and Firefox show me an error:

This client isn't compatible with the media and the server isn't sending a compatible media format.

I don’t know what the common thread is, because I get it with both 4K (HDR and SDR, H.264 and H.265) and 360p source material. I’ve only been able to find one video that plays at all so far: a 1080p H.264 SDR file (Profile High, Level 41, Resolution 1920x816, Bitrate 2000 kbps, Color space bt709) with 93 kbps stereo AAC-LC audio.

Jellyfin is set to disallow H.265 encoding, just to reduce the variables involved, and the number of threads is set to Auto. Hardware acceleration is off. This is all I get in the logs when I play a 404p H.264 SDR file:

Code:

[18:37:33] [INF] [123] Jellyfin.Api.Helpers.MediaInfoHelper: StreamBuilder.BuildVideoItem( Profile=Anonymous Profile, Path=/path/to/file.mkv, AudioStreamIndex=1, SubtitleStreamIndex=-1 ) => ( PlayMethod=Transcode, TranscodeReason=VideoCodecNotSupported, AudioCodecNotSupported ) media:/videos/5e6132ce-a415-b641-1f31-16b65f6d42e6/master.m3u8?MediaSourceId=5e6132cea415b6411f3116b65f6d42e6&VideoCodec=h264,h264&AudioCodec=aac,mp3&AudioStreamIndex=1&VideoBitrate=139616000&AudioBitrate=384000&MaxFramerate=23.976025&api_key=<token>&SubtitleMethod=Encode&TranscodingMaxAudioChannels=2&RequireAvc=false&Tag=140671401c8449abd745a381fd7fa2cc&SegmentContainer=ts&MinSegments=1&BreakOnNonKeyFrames=False&h264-level=41&h264-videobitdepth=8&h264-profile=high&h264-rangetype=SDR&h264-deinterlace=true&TranscodeReasons=VideoCodecNotSupported,%20AudioCodecNotSupported

[18:37:36] [INF] [125] Emby.Server.Implementations.Session.SessionManager: Playback stopped reported by app Jellyfin Web 10.8.13 playing The Movie. Stopped at 0 ms

There are no errors and there’s no ffmpeg command. There’s no separate ffmpeg log in the Logs section of the interface either. On the phone side, I can see the interface go gray with a loading indicator for a few seconds before the error pops up in Firefox; the same error appears almost instantly in Chrome.

My user settings have no limits on the channels, bitrate, etc.

(I searched for ‘compatible media format’ and found lots of threads, but when I follow the links, it tells me they don’t exist.)