
Yes. This has been theorized, but with the obvious limitation of building anything big enough to attenuate the sun’s output to a visible degree.
Right now we look for periodic dimming of distant stars, in order to ID exoplanets as they orbit and block light. We also look for any wobble from the gravitational pull of a large orbiting body, like Jupiter-sized things.
As for artificial dimming, that more or less falls under the concept of a “Dyson Swarm/Sphere”, and is something we’re keeping an eye out for too. Your signal concept would be carefully orchestrated windows in that swarm, as it orbits. But the energy and sheer mass requirements (measured in substantial fractions of whole planets) are at a level of civilization well beyond anything we can do at present. So there may be something out there, but we’re in no position to do the same.




This is just barely in the 1990’s, but The Conversatron comes to mind.
There was quite the cottage industry around Quake in the 1990’s. From GameSpy for finding matches/servers, to news and modding sites for which I can’t quite recall the names.
There’s also countless companies and startups that either went bust or were eaten by other companies.
Meanwhile, there’s stuff still online from then that has no right to be. SpaceJam comes to mind.