I just tested the NoRoot mannequin OP posted. You can actually get the animations to unreal without using Maya etc.
If you just upload the provided mannequin to Mixamo and export with the animation with skinned option/character, you can import the skeletal mesh + anim to UE4, then you can retarget the new animation to UE4 skeleton by right clicking the new anim sequence. Since bones and proportions match, you don’t have to manually setup anything and retargeted anim seem to work fine. I just tested this with one anim though but seems to work fine so far.
I tried to get the NoRootMannequin anims to stock UE4 mannequin with Modo but it didn’t give me the correct results (could be just my inexperience with animations on Modo), there’s few more clicks when you do it on ue4 side but it’s still fairly quick operation.