In the Transmission torrent client, you can set up selective downloads and enable sequential (linear) downloads. Sequential downloads will allow you to start watching movies or listening to music while they are still being downloaded.
NOTE: Important! Playing a file while downloading a torrent is possible via SMB/CIFS. DLNA server will be able to see the new file after auto-re-indexing the media library database, which will only happen after a complete download if a folder with torrent files has been added for indexing the media library. By default, the folder for indexing is set by the user.
The default behaviour for the BitTorrent protocol is to transfer files in chunks, allowing different pieces of files to be downloaded in parallel and providing fast, balanced downloads. But in the built-in Transmission torrent client, you can set the chunks to be downloaded strictly sequentially, from the first to the last. This will allow unfinished files to be played.
To enable sequential downloads for a torrent file, you will need to disable the "Append '.part' to incomplete files" option in the client settings:
And in the torrent attribute settings in the Config tab, enable sequential downloading:
Now let's check. The file is not yet fully downloaded, but you can run it for playback using Windows Explorer (or another file manager):