So yes, Doctor Doom does appear in First Steps. In the mid-credits scene, we jump four years into the future and see Sue Storm and her son Franklin reading together in their home in the Baxter Building.

As is usually the case with MCU movies these days, The Fantastic Four: First Steps includes both a mid-credits and a post-credits scene. And also sticking to the traditional formula, one is a goofy little stinger, while another has serious ramifications for the MCU.