Since 123D Design is no longer supported, Autodesk recommends transitioning to these currently maintained platforms: 123D Design - Intel app on M1 Mac - Apple Support Community
: It was originally designed for Mac OS X 10.7+ on 64-bit Intel processors. Autodesk 123d Design Download Mac
So, where does that leave Mac users? You have two options: scavenger hunts on trusted archives or utilizing the "last known good" installers from 2016. Since 123D Design is no longer supported, Autodesk