UPDATE: Your solution helped me a lot! Thank you for directing me to this video!! I ran into a minor snag with the now-deprecated “bone.bone.select” command, but I was able to contact the person who posted this video and get the control rig to drive my UE5 rig!
I’m sharing the updated “Fix Constraints” script I got from them here should anyone come across this post in the future with the same problem.
NOT MY SCRIPT, FULL CREDIT TO USER @/KLI ON YOUTUBE
UE5.8 → Blender 5.2
import bpy
Name of the armatures
rig_armature_name = “rig”
root_armature_name = “Armature”
Bone name mapping
ChatGPT is stupid, and calls all bones from the root armature root bone. READ THIS READ THIS READ THIS#
bone_name_map = {
“pelvis”: “DEF-spine”,
“thigh_r”: “ORG-thigh.R”,
“calf_r”: “ORG-shin.R”,
“foot_r”: “ORG-foot.R”,
“ball_r”: “ORG-toe.R”,
“thigh_l”: “ORG-thigh.L”,
“calf_l”: “ORG-shin.L”,
“foot_l”: “ORG-foot.L”,
“ball_l”: “ORG-toe.L”,
“spine_01”: “DEF-spine.001”,
“spine_02”: “DEF-spine.002”,
“spine_03”: “DEF-spine.003”,
“spine_04”: “DEF-spine.004”,
“spine_05”: “DEF-spine.005”,
“neck_01”: “DEF-spine.006”,
“neck_02”: “DEF-spine.007”,
“head”: “DEF-spine.008”,
“clavicle_r”: “ORG-shoulder.R”,
“upperarm_r”: “ORG-upper_arm.R”,
“lowerarm_r”: “ORG-forearm.R”,
“hand_r”: “ORG-hand.R”,
“pinky_metacarpal_r”: “ORG-palm.04.R”,
“pinky_01_r”: “ORG-f_pinky.01.R”,
“pinky_02_r”: “ORG-f_pinky.02.R”,
“pinky_03_r”: “ORG-f_pinky.03.R”,
“ring_metacarpal_r”: “ORG-palm.03.R”,
“ring_01_r”: “ORG-f_ring.01.R”,
“ring_02_r”: “ORG-f_ring.02.R”,
“ring_03_r”: “ORG-f_ring.03.R”,
“middle_metacarpal_r”: “ORG-palm.02.R”,
“middle_01_r”: “ORG-f_middle.01.R”,
“middle_02_r”: “ORG-f_middle.02.R”,
“middle_03_r”: “ORG-f_middle.03.R”,
“index_metacarpal_r”: “ORG-palm.01.R”,
“index_01_r”: “ORG-f_index.01.R”,
“index_02_r”: “ORG-f_index.02.R”,
“index_03_r”: “ORG-f_index.03.R”,
“thumb_01_r”: “ORG-thumb.01.R”,
“thumb_02_r”: “ORG-thumb.02.R”,
“thumb_03_r”: “ORG-thumb.03.R”,
“clavicle_l”: “ORG-shoulder.L”,
“upperarm_l”: “ORG-upper_arm.L”,
“lowerarm_l”: “ORG-forearm.L”,
“hand_l”: “ORG-hand.L”,
“pinky_metacarpal_l”: “ORG-palm.04.L”,
“pinky_01_l”: “ORG-f_pinky.01.L”,
“pinky_02_l”: “ORG-f_pinky.02.L”,
“pinky_03_l”: “ORG-f_pinky.03.L”,
“ring_metacarpal_l”: “ORG-palm.03.L”,
“ring_01_l”: “ORG-f_ring.01.L”,
“ring_02_l”: “ORG-f_ring.02.L”,
“ring_03_l”: “ORG-f_ring.03.L”,
“middle_metacarpal_l”: “ORG-palm.02.L”,
“middle_01_l”: “ORG-f_middle.01.L”,
“middle_02_l”: “ORG-f_middle.02.L”,
“middle_03_l”: “ORG-f_middle.03.L”,
“index_metacarpal_l”: “ORG-palm.01.L”,
“index_01_l”: “ORG-f_index.01.L”,
“index_02_l”: “ORG-f_index.02.L”,
“index_03_l”: “ORG-f_index.03.L”,
“thumb_01_l”: “ORG-thumb.01.L”,
“thumb_02_l”: “ORG-thumb.02.L”,
“thumb_03_l”: “ORG-thumb.03.L”
}
pelvis_name_map = {
“pelvis”: “ORG-spine”
}
Ensure we are in object mode
if bpy.context.object.mode != ‘OBJECT’:
bpy.ops.object.mode_set(mode=‘OBJECT’)
Deselect all objects
bpy.ops.object.select_all(action=‘DESELECT’)
Get the armatures
rig_armature = bpy.data.objects[rig_armature_name]
root_armature = bpy.data.objects[root_armature_name]
Enter pose mode for the root armature to add constraints
root_armature.select_set(True)
bpy.context.view_layer.objects.active = root_armature
bpy.ops.object.mode_set(mode=‘POSE’)
Parent bones from root armature to rig armature based on the name map
for root_bone_name, rig_bone_name in bone_name_map.items():
rig_bone = rig_armature.pose.bones.get(rig_bone_name)
root_bone = root_armature.pose.bones.get(root_bone_name)
if rig_bone and root_bone:
# Select the root bone
# Blender 5.x: selection state now lives on the pose bone itself
bpy.ops.pose.select_all(action='DESELECT')
root_bone.select = True
root_armature.data.bones.active = root_bone.bone
# Add Copy Rotation constraint to the root bone
constraint = root_bone.constraints.new('COPY_ROTATION')
constraint.target = rig_armature
constraint.subtarget = rig_bone_name
constraint.target_space = 'LOCAL_OWNER_ORIENT'
constraint.owner_space = 'LOCAL'
print(f"Parented {root_bone_name} to {rig_bone_name} with Copy Rotation constraint")
else:
print(f"Bone {rig_bone_name} or {root_bone_name} not found")
for root_bone_name, rig_bone_name in pelvis_name_map.items():
rig_bone = rig_armature.pose.bones.get(rig_bone_name)
root_bone = root_armature.pose.bones.get(root_bone_name)
if rig_bone and root_bone:
# Select the pelvis bone
# Blender 5.x: selection state now lives on the pose bone itself
bpy.ops.pose.select_all(action='DESELECT')
root_bone.select = True
root_armature.data.bones.active = root_bone.bone
# Add Copy Location constraint to the pelvis bone
constraint = root_bone.constraints.new('COPY_LOCATION')
constraint.target = rig_armature
constraint.subtarget = rig_bone_name
constraint.target_space = 'WORLD'
constraint.owner_space = 'WORLD'
print(f"Parented {root_bone_name} to {rig_bone_name} with Copy Location constraint")
else:
print(f"Bone {rig_bone_name} or {root_bone_name} not found")
I’m not an expert, and I have only used a self made control rig for UE animations. But does this video provide any answers?
The description of the video tells about minor patches to the rig after recording the video, did you also check those? 
Also it seems to have a link to a drive folder with the project files.