We have plans for how one would modify the Sun. The physics is fine. The machines are enormous.
But over all we expect intelligent life to be able to spread to other planets, we expect them (and us) to capture more than their planet’s share of their star’s energy
But we see no evidence of it happening
So really there are two options
It’s too hard to use enough energy to be seen; or
There aren’t other intelligent species in the observable universe, at least none that can reach space
If life could do the things you think it might, our own galaxy would already look a lot different compared to what we’re seeing.
We have plans for how one would modify the Sun. The physics is fine. The machines are enormous.
But over all we expect intelligent life to be able to spread to other planets, we expect them (and us) to capture more than their planet’s share of their star’s energy
But we see no evidence of it happening
So really there are two options