In brief, it does not appear to be possible (at this time) to re-target existing animations to a MetaHuman. Using this tutorial, for example – in Retarget Manager > Modify Pose, only poses are available for specific body parts – no full body poses, thereby making it necessary to select “current pose”. There really is no other option.
The bones show up properly when re-targeting a blueprint / animation:
But as soon as re-target is hit, it’s clear the mappings are skewed, regardless of the humanoid defaults, with arms stretched across each other all the way to the ground and shoulders scrunched up to the top of the head. I am fairly new to this side of UE, so it could be I have misunderstood the procedure. But if you follow the tutorial linked above, as closely as possible, the re-target will not run successfully. Is there any way to get this working, or will we have to wait for a fix / update?
All in all, a very bad first impression. If the problems stopped at re-targeting, I’d be quite impressed with your amazing promotional materials for UE5 — but very basic things are broken. For example, if you migrate an asset from another project and add it, delete it, then put something else in the scene, it doesn’t matter how many times you save and compile, you will never get rid of that asset. It will forever be present in play mode. These are very basic things. I am surprised they escaped quality control prior to early release.