I decided to use mixamo skeleton as parent in my project instead of UE mannequin. So nothing changes, generally. Dunno how others are stucked into mesh distortion. I use just generic fbx export from mixamo, аnd the only issue I had, sometimes character is rotated incorrectly.
also, unreal retargeting still works, but you need to make very similar ref poses and next retargeting setup for mixamo skeleton. уеs, there’s no root bone selected , it’s the only way to make it work. also HIPS should be set to Animation translation, other bones to skeleton