Hi there,
I haven’t tested, so I am not sure if this is really helpful. The only “offline” converter I know, which is NOT compatible with UE5/metahuman, is this one:
UE4 Marketplace - CSV To Animation Tutorial - YouTube
CSV Animation Converter in Blueprints - UE Marketplace (unrealengine.com)
It uses the animation exported as CSV to create animation curves, but it only works with characters with FACS ARKit. Perhaps you want to contact the seller and address your questions.