[Sebb767]

Many, actually. There are quite a few active alternatives now, such as Nebula for science YouTubers and Odyssey. Last I heard Linus Sebastian was working on an alternative as well.

It seems that most content creators are quite worried about the way YouTube handles (de-)monitization and copyright strikes. Many CCs are also streamers and use YT only as a side channel. Sure, YT still has a large footprint, but it's not as solid as it used to be.

[AshWolfy]

There are, but generally for specific interests, and not nearly enough to challenge youtube's market domination. Without something dramatic youtube effectively has monopoly control of supply and demand.