[Kyng]

Isaac Arthur is the first one who comes to mind. He makes rather long videos (often 30 minutes or more) covering what humanity might be like in the far future. He tackles a variety of aspects of this topic: what technology we might use; how we might live our lives; and how far across the galaxy we might explore. Another popular topic of discussion on his channel is the Fermi Paradox (essentially: if the universe is billions of years older than Earth, why didn't some other alien civilisation emerge and conquer the galaxy billions of years ago?). He has a whole series of videos outlining possible solutions to this paradox, and explaining the merits and shortcomings of each one.

It's certainly not for everyone, but if you like his content, then you'll probably love it.