Check out OpenVAT, a Blender add-on developed by the creator Luke Stilson, also known as sharpened, that encodes Vertex Animation Textures directly from animated geometry. The tool is created for real-time engine support and is compatible with engines such as Unreal Engine, Unity, and Godot.
VAT, or Vertex Animated texture, is a texture where pixel data stores vertex positions (and optionally normals) per frame. The add-on supports frame-based geometry via Geometry Nodes, packed or separate normal texture output, arbitrary attribute encoding, auto-setup preview scene and cleanup, a high-quality PNG or EXR export, and verified extension on the Blender Extensions platform.
To learn more about Vertex Animation Textures, you can watch this video and a playlist with the content from the add-on creator and other artists: