For the record; I adhere to the electric/plasma universe theory (more precisely plasma/fractal universe theory).
Impossible to see directly.
Very observable indirectly, we can see the orbits of stars near out galactic center. We know they are orbiting something VERY massive and small, and black.
We can see matter compressing and heating up as it tries to all fall into a tiny spot, like all the attendees in a flaming theater trying to get through a single door.
We can see gravitational lensing of background stars and galaxies that happen to to be in the same line of sight.