Blarg! 🙄 it seems there's an I-beam or something above the plaster, so I can't drill, any existing holes are useless, and "glue instead of screw" fails miserably, so we're left with a lighting fixture dangling from the ceiling.

It WAS a bare bulb dangling from a wire, so it's still an improvement... Kinda.

I guess the next step is call in a pro.