I don't know if twitter will replace youtube or other outfits until they get more independent and Google/Apple can't hold them hostage with the app stores. That is something I hope Elon can work on.
As far as youtube alternatives, I am hearing people say that Rumble has been doing a great deal to set up their own independent infrastructure to support their site. A number of people I watch are getting good view numbers over there and they are starting to pay out ad revenue. IMO, they still have some user interface issues to work out, but I hope they do well. Youtube has a big head start so it isn't something happening soon.