Synchorize downloaded anim pack mesh to UE default manneqin (created when a project is 3rd person):
Download the anim pack ass of mannueqin, delete its skeleton, click replace
IK Bones - Retargeting
Go to Rig folder, open TRG UE4 to UE5 IE retargeter
Now, those anim pack should be there.
Click Chain Mapping, Root, then change FK Adjustments to Globally Scaled
Click set Browser, click wanted animation, exported Selected animations