My company has been asked a number of times to help some of the UAM folks to design a ducted fan propulsion system for their air vehicles.
Our designs are quieter, more efficient and safer than open or even shrouded rotor blades.
We won't do it because of the certification issues and liability exposure.
I have been involved with Unmanned Systems since 2002 so I am very familiar with the UAM concept for both passengers and cargo. I have no issues with the reliability, functionality and safety of UAS I just don't think we will see unmanned UAM vehicles for quite some time.
I could go into chapter and verse but I won't.
We did a concept analysis for UAS cargo vehicles, fixed wing, to service under used small airports (essentially getting mail, packages, etc. off the road and into the air) and it made complete sense but that is not what we do.
We also did a ducted fan design for Honda - essentially a flying motorcycle, but the lawyers, who, like the engineers, liked the design, said NFW.