my real identity is: a human with functional eyeballs
which is why I can look at this and tell you that Lumen is the worst real time GI tech in the industry
(watch in 4K)
low ray count + low precision BVH:
Lack of Screen Space information when too far away as well as obvious light leak and denoiser boiling.
weird brightness changes due to lack of screen space information for secondary bounces, as well as specular highlights flaring up in the dark due to reflecting a bright cubemap while Lumen tries to react to the changing camera to fill the gaps where you see those white sparkles:
another example of reflection ghosting.
one issue that happens from time to time with Software Lumen, is that some scenes just go full darkness due to the lack of screen space information for secondary bounces. you saw this partly in the third video above.
Once the screen space information is gone, the entire GI just blacks out as no primary light bounce is visible anymore for it to create ambient lighting.