Importing the character from Blender to UE5 is more involved than simply dragging the FBX file into the editor. We have to setup automated twist bones with a Post Process Animation Blueprint running a Control Rig.
Unfortunately at the time of this writing seems to be a bug in UE5 that can cause the editor to crash when setting a Control Rig on the character. This is an editor side issue unrelated to Uefy.
In the video above At 0:51 I create the Manny89ControlRig and at 1:22 I open it and import the correct bone hierarchy. At 5:01 I set the Default Animation Rig to this control rig BEFORE I set the Post Process Animation Blueprint.
By correctly creating the control rigs and post process anim blueprint and setting them in the correct ORDER I avoid the crash and everything works out.