I’m late to the party, but I found that the issue is the retarget poses do not match up. The hands in the MANNY RETARGET POSE are straight, while the hands of the UE4 are slightly curled. If you change to DEFAULT, the hands of MANNY (UE5) will match.
Of course, you can make the MetaHuman compatible with the UE5 skeleton, and boom, there it is.
Look in the TOP LEFT.
BEFORE:
AFTER:
