I’d be interested to know this too. I’m not interested in the mesh so much as the default Unreal skeleton. It would be nice to be able to create a character that works nicely with Unreal, but then use it in other contexts too.
There are lots of free humanoid rigs: several come with Makehuman, and there is also the Rigify rig from Blender. Any of these could be used, but then the character would be a bit inconvenient to use with Unreal and its standardised animations.