What is beyond the farthest galaxy?
We don't know
There are many tales that people believe is out in our universe.
I heard that outside our solar system are millions of other galaxies. Maybe there is another place that is exactly like Earth.
We will never know unless someone goes out and comes back and tells us. However we will never know because by the time that someone comes back, they will die in the spaceship of old age. It would take 100,000 years to cross the Milky Way at the speed of light but it is impossible to reach that speed. we know that it take about 2 years to get to Mars and 9.5 years to get to Pluto to the other.
Over all, Nobody has ever seen past the farthest galaxy let alone getting there.