Fix OptiTrack to Unreal Engine mocap import (FBX animation issues)

I recently completed a 3D skateboarding motion capture session using an OptiTrack system at a studio in Dubai (Greysea Studios). I received around 61 FBX files exported from Motive (the OptiTrack software), containing motion capture of skateboarding tricks and movements.

However, I’m having trouble importing these FBX files correctly into Unreal Engine 5.5 / 5.6.
When importing, Unreal either:

Doesn’t recognize the skeleton/animations properly,

Or requires a mesh bound to the skeleton before it allows import.

I’ve tried fixing this through Blender by binding a simple cube mesh to the skeleton (to generate a skeletal mesh), but Unreal still doesn’t import the animations correctly or visualize the skeleton the same way as in Motive.

At this point, I need an expert who can help me properly import and visualize my mocap data in Unreal, ensuring the skeleton, animation, and timeline work as expected.