hi @FXHochban
First off i fully admit ive not delved into the Lyra project so im not sure what they are using in it or whether it has any custom C++ modules to do this.
But firstly there are 2 plugins in unreal Full Body IK and IK Rig. Check those are enabled (think they are by default but best to check)
Other than that i have seen a youtube video that does a convincing job of this with another plugin:
Unreal Engine Tutorial | Inverse Kinematics (IK) & Foot Placement (works in UE5) - YouTube
it uses the Epic Power IK full body Ik solver and is free in the market place
Power IK in Code Plugins - UE Marketplace (unrealengine.com)
looks very good indeed!