How to completely disable transcoding on Android TV and Android phone's clients?

[TheDreadPirate]

Depending on the kind of subtitle, they may need to be burned in. That is assuming you are using the integrated player. AFAIK, ASS and DVD/VOBSUB always need to be burned in for exoplayer (the integrated player). Though, work on adding ASS sub support is in progress.

If there is transcoding or remuxing, skipping around will be slow depending on your server specs as ffmpeg needs to restart the transcode/remux if you skipped to a segment that hadn't already been transcoded.

Also keep in mind that transcodes are written to disk. So the speed of the disk also factors into how responsive seeking is for transcodes.

As for remembering the video position, if you use an external player, like VLC or Nova, playback tracking is not supported except for video completion (watching all the way to the end). It will not track partial progress. However, I recall someone saying that MPV as an external player DOES support playback tracking. Which would make sense, if true, since we use MPV as the playback engine for Jellyfin Media Player on desktops.

If you share your jellyfin logs via privatebin.net we can get an idea of what playback method Jellyfin is using for some of what you're describing.