I created this tech in Unreal Engine 4 in 2018 (Lumen didn't exist yet). It leverages the engine ray-marching system used for distant shadow.
It simulates real-time reflection and a simplified global illumination without using ray tracing or SSR.
The selling point is its performance. The demo runs in 6 milliseconds on a GTX 970, so it can also be used for VR applications.
Indirect lighting isn't very flexible, but real-time reflection is, and it's better suited for studio lighting setups and design renders.
I will consider releasing it on the Marketplace if it meets interest.