Lumen is not broken in 5.0, that particular Demo is.
I couldnt get Lumen to work there either, while I have it working for almost 9 months now in a bunch of other Projects.
In fact, it is so broken int hat project that even the Lumen visualization doesnt work…
PS: Yes, i turned it on in the project settings, the post process volume, built the mesh distance fields, no static lighting, sun is movable etc… no idea why it isnt working.
Just use something else to play with lumen, but not that Sun Temple demo (or its spatial audio copy).