Taking a different tack with the alien hypothesis.
Interstellar travel is hard, really hard to do in any organic lifeform's time frame.
So you've got a stable civilization, no where else can readily get to/communicate with in a usable time frame, aside from an occasional colony ship.
How do you preserve yourself long term? Stellar engineering.
Red dwarves last magnitudes longer than larger stars, so you siphon off enough mass to reduce your star to a red dwarf and greatly increasing it's life span.
Use all that hydrogen you draw off to power things like moving your world inward to the new habitable zone, terraforming, or even creating, new habitable worlds in the new zone, or even build a colony world fleet big enough to carry everybody and their future offspring to another star when this one fails.
All this is going to take centuries, if not thousands of years, and the machinery involved isn't going to be small, and the orbiting clouds of by-products, raw materials, new construction, whatever, isn't going to be small either.
(Probably on the scale of when the Mark I sunsucker becomes obsolete, you just start terraforming it, or converting it into a colony ship.)
But it's probably only just a poorly fusioning star, and not aliens, too bad. :(