I want to be able to track an image, and then display a UI Widget Blueprint on top of it. Is this something that’s possible/supported in Unreal Engine?
Yes, no problem.
Please notice that UI Widgets are 2D in screen space.
Tracked images will be in 3d space so instead use a “Widget Interaction Component” for that.
You can learn about these here in the documentation: Widget Interaction Component | Unreal Engine Documentation
Example on YouTube by Mathew Wadstein: WTF Is? Widget Interaction Component in Unreal Engine 4 ( UE4 ) - YouTube
Good luck!