Todor Nikolov writes:
ExpyKit is a free, feature-rich addon for Blender that can act as a bridge between Rigify, Mixamo, Game Engines, DAZ3D, etc.
The workflows that it enables are far too numerous to cover in a single tutorial. Therefore, I'll focus on using ExpyKit to retarget Mixamo animations to a Rigify rig.
This is already possible with tools such as Rokoko or Auto-Rig Pro but ExpyKit is very fast and streamlined. It even has an operator that automates the process of retargeting multiple mixamo actions in one go. (you can retarget dozens, even hundreds of actions with a couple of clicks!)
I think you'll like it.
You can download Expy Kit here.
ExpyKit was developed by Paulo. Here are links to his social media: YouTube, Instagram, Twitter