Hello!
For some reason, the 3D view in the editor has turned completely grey, regardless of what scene I'm in. Specifically, it seems to be the sky refusing to render or illuminate the scene. It remains this way regardless of whether I have a WorldEnvironment node in the scene (though the WorldEnvironment node can affect the lighting a bit, such as enabling SSR). It's only like this in the editor--the game itself looks fine when I play it. (It's also only in this project: other projects are fine.)
I don't know why this is. I didn't intentionally do anything. It happened randomly--one minute everything was as you'd expect, with skies and HDRi backgrounds and the like, and the next, GREY.
Is this a bug, or did I just change a setting and not realize it? Does anyone know a way to undo this?
Example images:
A simple 3D scene with a single MeshInstance (sky is completely grey)

The same scene with SSR enabled (even the meshes turn grey)

Turns out it was a side-effect of "transparent background" in the project settings. If anyone else gets stuck with this, well, here you go I suppose!