First Steps' includes two post-credits scenes. Here's how that big reveal sets up what's coming in Phase 6 of the MCU.

Doomsday connects to The Fantastic Four: First Steps? A key mid-credits scene introduces a mysterious presence, hints at a growing multiversal threat, and sets up one character’s deeper interest in Franklin Richards.

First Steps has a reveal that should tide them over for a while. Following the post-credits stinger in Thunderbolts* that was directed by the Russo Brothers, the Fantastic Four have now arrived in the MCU.