A editor script to automatically apply the recommended settings from Synty Studios (see https://www.youtube.com/watch?v=9H0aJhKSlEQ) to ensure that Animations imported from Mixamo work with Synty characters. It additionally (optionally) renames the animation clip according to the name of the imported asset to avoid multiple animations with the name mixamo.com.
SyntyMixamoRigger.cs simply configures any .fbx added to Assets/Animation/Animations/Synty/Mixamo/ with the recommend values. This includes character rigging.
Then, SyntyMixamoAnimationRenamer.cs renames the animation clip mixamo.com according to the filename of the asset and removes any other clips. If you do not want this to happen, just remove SyntyMixamoAnimationRenamer.cs.
Simply download the repository and place it's contents right into your unity project directory.
Download an animation from Mixamo with the settings/character described in the tutorial.
Then just place the downloaded .fbx into Assets/Animation/Animations/Synty/Mixamo and move any Mixamo animations used on Synty models into that folder/trigger a reimport.