“How Close Can a Black Hole Be to Earth?” from Riddle (10 min), Sept 6, 2021.
The video mentions that many smaller black holes are effectively parts of binary star systems. The closest is about 7000 light years from Earth (there are about 20 known in the Milky Way.
But because you can’t see a black hole, could one be relatively close and not be detected? Probably not because you would detect gravitational effects.
The probability of a black hole nearing the Solar System is thought to be about one in one hundred billion years, seven times the age of the Universe.
Picture: Wikipedia embed, black hole seed, click for attribution.