Cool! Mine passively extracts unlimited energy from the expansion of space.

Not scientifically perpetual. But definitely, relative to the finite future lifetime of the human race, operable for perpetuity.

And by extracting dark energy, we can not only turn the big rip around. But by pulling dark energy out of space in a linear direction ahead of a ship, we can power the ship to high speed, as we contract space in front of the ship. Like fusion, we can use extracted dark energy to extract more dark energy. Essentially smoothly teleporting forward. No more fundamental speed limits relative to observers at distance. Looking forward to exploring beyond the observable universe.

It isn't "free" though. There are unique risks.