The official download page only allows for download of 1.21 and above.
https://www.reallusion.com/auto-setup/unreal-engine/download.html

I was hoping to find older versions on the update page:
https://www.reallusion.com/auto-setup/unreal-engine/update.htm

But no, only info and no download buttons.

Why do I need a version that's so old in the first place?

The project I am working on is developed with Unreal version 4.21 and the only versions of Auto Setup that work with UE 4.21 are 1.01, 1.02 and 1.03, which I can't seem to find.

Any help is appreciated.