Life, yes. Intelligent life, yes. Intelligent life whose manifestations we can recognize, no.
That said we could probably recognize it via traces and I’m sure we’re about to confirm it’s existence.
I will add that "not alone" also implies we are able to be aware of "them" as they currently are, not billions of years ago.
Put differently, if we discover signs of a civilization OR even traces of something akin to life, but we cannot validate they still exist, we are still alone.
In some ways emotionally, I’d prefer the archaeological previous advanced civilization discovery that both confirms: We’re not alone in the extent of time, but we don’t really have anything else to consider in the present, so we can study and learn from something static.
Though I feel, optimistically, I guess, that the reality is more dynamic than that.