The 2nd point does occur normally, but the fix suggested should work. With Lightmass (baked lighting) GI is enabled, so the lighting system will calculate bounces around the scene, however moveable / dynamic lights do not support high-quality GI without a huge impact to performance, so with a single light alone shadows will appear solid black. You can circumvent this by using a skylight, but skylights don’t support isolated use cases (people say you can use the shadows generated by a skylight to isolate it to outdoors environments, never works for me) so you’re forced to either not use a skylight, use it with a low intensity and deal with the visibility indoors without light, or leave it at high intensity and have indoors be ultra bright. I use a directional light pointed down to soften ground shadows, but wall shadows and any shadow not along the ground / objects on the ground are still solid black.