I use Simple Audiobook Player by mdmt. I like it, because it browses the directory-structure and is pretty minimalistic.
It has two pretty bad shortcomings
- it is not FOSS (one of maybe 3 non-FOSS Apps I use)
- playback speed control is a pro feature.
- can not play .wav
It has a pro version, but never brings it up (no nagging).
That is what I do for most German movies. It only takes half a minute so get the audio-video delay right at the beginning.
And maybe 1/30 movies will not work, because the sources have different pacing.