add example to download video with multiple audio streams

public/en/youtube-downloads-with-yt-dlp.gmi

@@ -18,6 +18,42 @@ yt-dlp CHANNEL_URL|PLAYLIST_URL|VIDEO_URL -S res:1080
 yt-dlp CHANNEL_URL/playlists -o '%(uploader)s/%(playlist)s/%(title)s.%(ext)s'
 ```
 
+## Download video with multiple audio streams
+
+* tested on yt-dlp v2025.12.08
+
+### Download best video, best audio (original + uk) and subs
+
+``` bash
+yt-dlp -f "bv+ba+ba[language=uk]" \
+        --audio-multistreams \
+        --embed-metadata \
+        --embed-subs \
+        --all-subs \
+        --merge-output-format mkv \
+        URL
+```
+* it's important to provide the `--embed-metadata` flag to prevent all audio options from being marked as 'English'
+* the `--merge-output-format mkv` argument is recommended, as the MKV container provides the necessary features for built-in audio and subtitle options
+
+### Fix audio stream names using post-processing
+
+If the `--embed-metadata` argument is missing, you can fix the names for audio options after by using ffmpeg:
+
+``` bash
+ffmpeg -i input.mkv \
+       -map 0 -metadata:s:a:0 language=en -metadata:s:a:1 language=uk \
+       -c copy output.mkv
+```
+* it's important to keep the previous `-f` order
+
+or just inline:
+
+``` bash
+yt-dlp ... \
+       --exec "ffmpeg -i {} -map 0 -metadata:s:a:0 language=en -metadata:s:a:1 language=uk -c copy output.mkv" URL
+```
+
 ## Extract audio
 
 ``` bash