There is a catch-22 that helps YouTube keep it's monopoly. Nobody will jump to another platform until all their favorite creators/majority of media is there, but no other platform is able to attract a significant portion of creators/media until they have a large base.

Systems that enable multi-platform natively are the answer to change the calculus on this problem. End-user clients such as Grayjay that enable users to view videos from multiple platforms at once can give much-needed views to creators on alternate platforms. A similar solution for creators (not sure if one exists or not) would lower the barrier to upload to all platforms at once.

That phenomenon is called network effects, if you’d like to read more about it.

The solution that will actually work, then, is to build a platform that has the YouTube content. Don't try to convince creators to sign up for your new multiplatform thing - just rip it directly from YouTube. Now you're thinking like a VC-backed startup. Yes, it's illegal, so make sure to scale rapidly and become rich before they have time to sue you. Facebook did this to Myspace. Doordash did this to restaurant phone orders.

Have you heard about Russia? Why bother of doing multi-platform if they can just prohibit anything Western and build their own digital platform for everything.