EyeDome lighting problems with parallel rendering
We're having problems with eye dome lighting again in 5.6.0 when using parallel rendering. This was apparently fixed in !2217 (merged). The original ticket for that is #17971 (closed).
I did a bit more testing with your grizzly build of v5.6.0-osmesa and it looks like EyeDomeLighting is present ONLY if connected to a single PE. With multiple PEs EDL shading is missing (even though the plugin is loaded). As I recall this was a flaw in some earlier version, perhaps on or around 5.5.0 – so it may be possible that the repair was not correctly brought forward into version 5.6.0.