Nebula has been quite successful as far as I can tell. A whole bunch of educational YouTubers have moved over or were part of establishing it and honestly it works well. Videos can download to your device, the quality is the same, the app is a tiny bit janky but nowhere near as bad as all the ads etc on the YouTube app, and the cost is actually reasonable and goes in a reasonable share to the creators. I strongly prefer direct access to creators like this and also like on Patreon. Direct support means there is no advertiser in between to demonetise a video or have it taken down because it is controversial. You can’t even have a WW2 documentary on YouTube but you can have actual Nazis, but on Nebula you get analysis and history without Nike or Surfshark being reticent to sponsor a video.
Yeah, they have a bunch of smaller creators there too. Honestly their internal business structure seems much more mutually beneficial than something like YouTube could ever be. All of the creators that I watch who are on Nebula I watch exclusively there now and that has taken a good 40% of my YouTube time away. My current favourite is Stefan Milo who talks about paleoanthropology, basically how we can know about human prehistory and evolution. There was a great video about tracing the genetics of South American populations to figure out when humans arrived on the continent and where from, such interesting stuff.