Hi,
May be it's (summer)TIME to rename ADM 'Output format' bottom left field to the proper tag, i.e.: 'Container' (or 'Output container'),
as it lists no VIDEO format whatsoever but, obviously / necessarily, video containers (only).
OK: we know that '.mkv, .mp4, etc.', are FILE formats. Nevertheless, since they are no VIDEO formats, it's confusing to many a beginner...
[ In other words, less misunderstanding of what we manipulate would save them (& I) some time... ]