[extractor/youtube] Subtitles cannot be translated to `und`

Closes #5674

diff --git a/yt_dlp/extractor/youtube.py b/yt_dlp/extractor/youtube.py
index 79d082d0be3ce7b3db1f8fbb989e8dfee84ce517..c6c89915b41aff7b7acb278b81abdd804cb4ca0c 100644 (file)
--- a/yt_dlp/extractor/youtube.py
+++ b/yt_dlp/extractor/youtube.py
@@ -4085,7 +4085,7 @@ def process_language(container, base_url, lang_code, sub_name, query):
                     if not trans_code:
                         continue
                     orig_trans_code = trans_code
-                    if caption_track.get('kind') != 'asr':
+                    if caption_track.get('kind') != 'asr' and trans_code != 'und':
                         if not get_translated_subs:
                             continue
                         trans_code += f'-{lang_code}'