Like what is the ultimate fate of the voyager probes and others on escape trajectories? My understanding is that space is far too sparse for these things to ever hit anything by coincidence, so their eventual fate is probably to be ejected out of the galaxy at some point.

They are then unlikely to be moving fast enough to actually cross intergalactic distances quickly enough for the expansion of space to not outpace the distance covered, leaving them in this void forever.

How long would they be recognizable as technological objects before the eons worth of stray hydrogen atoms erode everything away?

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[–] Xavienth@lemmygrad.ml 4 points 4 days ago

It may seem like the Voyager probes are declared to have reached interstellar space every now and then because there are different boundaries they had to pass through. Of note, there's the termination shock boundary, and there's also the heliopause. There's also two probes, so you'll hear twice as many declarations.

Really, though, they both are in interstellar space. They are out of the heliopause and are receiving an increase in cosmic rays indicative of being in interstellar space. Voyager 2 also has the capability to measure solar wind, and its measurements dropped around the same time cosmic rays increased. Voyager 1 entered interstellar space in 2012 and 2 in 2018.

Source

For your viewing pleasure, here's a graph of cosmic rays over time for both probes, and a distance scale is provided at the top for reference.