My little tutorial video is of course nothing new. Epic made a video about Mixamo characters some time ago:
https://.com/watch?v=xy9aLbZLdeA
My video is basically a clone of Epic’s video. Doesn’t matter which one you watch, both show that Epic new skeleton retargets normally with no problems.
Anyway, if you ever get stuck with something in UE4, just visit Epic’s channel. There are hundreds of tutorials there.