The volumetrics plugin that ships with Unreal has an example of this, essentially it builds a pseudo-volume texture in a regular render target instead of a “real” volume texture.
From what i understand though, it is slower to use than a real Volume Texture, which is a feat in itself because capturing a volume texture at any useful resolution in realtime is already insanely slow. Also you also can’t generate mipmaps…
The example is the “Voxelize Meshes” map in the volumetrics plugin content folder