In the center of our galaxy, there is a supermassive black hole. I have little doubt of that.
Say, that you go there. It will take about 25000 years according to our Earth clocks, and less than say, 100 years according to the travelers’s clock.
What will you see there, on the other side of the event horizon of the central black hole?
Don’t worry, you won’t necessarily die there, crossing the surface of the central black hole’s horizon.
It could be, that you will see another, smaller black hole, orbiting and swallowing a big star, which (the star) has another black hole in its center! Maybe you’ll only see one million or so ordinary stars of all types and many neutron stars orbiting around each other.
What is a black hole from the inside? Maybe a giant “solar system” with millions of stars and even more planets and gas clouds orbiting each other. No singularity anywhere.
It’s possible that there are only stars inside a black hole! And some pulsars or neutron stars, perhaps. And some smaller black holes, too. Some of them might be nothing else than a lot of stars, again orbiting around each other!
It’s very much like frying eggs on a frying pan. Breaking one egg, usually means seeing the yoke and the white. But sometimes there is another egg inside. I am sure you have seen this on youtube.
In the case of black holes, it’s just much more diverse. A black hole may have a lot of stars inside. And a star may have a black hole inside. And a planet, which could have a black hole inside.
It’s not necessarily all black inside the supermassive central galactic black hole!