Why Jellyfin doesn't just 'work'?

[Armano]

Actually my happiness was premature.
The issues are solved only if on the client (Android TV) I will choose the Automatic player, if I change to Exoplayer the issue is as it was before.
My server is set for Hardware acceleration via Quick Sync.

While it would make me little difference what player is used by the client if the libVLC would support changing the scaling of the video. I like to streach videos to 16:9 ratio to use entire screen - but I see libVLC doesn't have such option?