I love stuff like this. If you do too, then I highly recommend this incredible youtube video of the end of time: https://www.youtube.com/watch?v=uD4izuDMUQA&ab_channel=melod...
Serious question: wouldn’t all mass that had time to gravitate towards and convene into galaxies, stars and black holes been drifting too far apart by then to be even remotely close for their gravities overcome these - then - unimaginable distances?
Galaxies which are not gravitationally bound won't encounter each other, so it doesn't end up merging the whole universe into a single black hole.