What would the call sign of a non-standard aircraft carrying the US President be? So, it's well known that the government planes operated for the US President are called Air Force One; less well-known is that this is a call sign given to any Air Force aircraft that carry the president, and that if the President rides in an aircraft owned by another branch of the US Armed Forces, they would become known as Marines One, Navy One, or Army One, while any civil aircraft that carries the US President becomes Executive One.
What about aircraft that are exceptions to the normal FAA rules for aircraft licensing, however? If the US President was riding in (or piloting) a glider, ultralight, or autonomous drone taxi, what would their call signs be, if any?
This question is unanswerable in its present state. A glider is a certified and registered aircraft in the US. Ultralights are not register aircraft in the US. And, they are not typically in contact with ATC. Autonomous drone taxis have yet to receive FAA certification, airworthiness, and registration. So, the best manufacturers can do with drones at this time is to fly them unmanned or on test flights.
The bigger question is whether the Secret Service would allow the president to pilot any aircraft. Let alone fly in a non-certified, unregistered aircraft. After all, they do not allow the president to drive a car while he is in office.