Hi @RadicalResearcher - Welcome!
I mentioned this on Paranormalis, but something akin to time travel archeology. Send a small drone or other undetectable technology back in time, somewhere desolate where entry/exit isn’t going to affect anything, fly to that location, record events, and then report back home with their findings.
Thinking about it now, I’m not sure how you’d achieve that without altering things even just a little… Preventing a bug from wandering this way or that. Any change would send you back to a different worldline so you’d have to figure that out, but as a practical use I think archeology and making efforts to understand our origins would be the best use.