The black hole eating stars, one by one.
If you were going to put a signal (that was also a puzzle to be unlocked), seems like the center of the galaxy would be a good place to make it emit from. Kind of obvious place to look.
But yeah, would almost certainly fall into the black hole in the center in a couple million years or whatever.
Is the signal's data available publicly? I wonder what the cryptanalyst community would think of it.
I would think that a intelligent species capable of placing a galactic billboard at the center of the galaxy would be intelligent enough to encode their message in an easy to decipher manner. Although, what does "easy to decipher" mean to a species with that technology. They may have stopped using any form of language that we would understand, generations ago.
Is math a universal language? Could an alien species use a number system that we wouldn't recognize?
There is an open access version at ArxiV.org: https://arxiv.org/pdf/2109.00652.pdf