Why MKV may not work everywhere
MKV is flexible and popular for archives, but many websites and lightweight players prefer MP4. The issue is usually compatibility, not the video itself.
Why MP4 is the practical output
MP4 is accepted by most upload forms, phones, browsers, and sharing apps. Convert MKV to MP4 when the destination rejects Matroska.
What to check
MKV files can contain multiple audio tracks or subtitles. After conversion, confirm the expected audio track is present.