Metric expansion only has an effect on structures larger than galaxies, so there should be no difference in 20by as a result of it. Eventually if it continues distant galaxies will redshift to black, but the Milky Way itself won’t be torn apart.

Everything will have changed long before then: https://en.m.wikipedia.org/wiki/Andromeda–Milky_Way_collisio...

In 20B years, HN users would be seeing this in their mind's eye !

We'll be to busy preparing for the next big thing, in 20 billion years VR will be just a couple of years away.