So I wonder, where are these giant black holes now? There should be some closer to us than at the edge of the universe, unless something happens to them.
Sagittarius A* is "merely" 26 thousand light years away (but we probably won't be imaging it, since there's a lot more in the way)
The M87 supermassive blackhole is thousands of times as massive as Sagittarius A*, but since Sagittarius A* is a lot closer their emission rings appear roughly the same size in the sky (42 μas vs 51 μas). Both have already been imaged by the Event Horizon Telescope. https://en.wikipedia.org/wiki/Event_Horizon_Telescope