I wonder if some kind of pledge system would work. Similar to Patreon, but instead of paying immediately or paying monthly, you simply make a pledge that if such-and-such creator starts uploading content to such-and-such free platform, then your pledge for $x amount goes through (either monthly or one-time). There's no actual money changing hands or any actual commitment to do so, until and unless the creator in question comes onboard. Sort of like a bug bounty, multiple people could make individual pledges to build up a pot of money, that the creator could then cash in. I can see some avenues for potential abuse, and of course people can just cancel once "mission accomplished", and you've got to expect some level of that happening but assuming creators and their community have a good and supportive relationship and really are trying to support each other I don't really see that being too much of an actual concern.

We need something that helps make the case to creators that there is a real market for this, that there is a path to being compensated for their work, and that those parts of their community that are interested in this will still help support them. It doesn't even necessarily have to be directly competitive with Youtube, at this point, we're not going to collect millions of dollars. But it shows that there is potential money being left on the table, and even if it's only a little bit of money, it's not much work for a little bit of extra money, and the creator will ultimately have to decide whether that work is worth the extra money.

Right now, there's no guarantee at all, and in fact there usually is no financial benefit. They're just guessing whether there might be some money down the road for them on alternative platforms, and that's a pretty tough sell for anybody, nevermind somebody making millions already.