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.

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.