alt Hacker NewsI heard that main source of income for some professional YouTubers are Patreon and sponsorships. Ad revenue is dead last and very unstable. Also, if you are building your business on single platform, which one day might decide that your content does not adhere to their rules - that's a high risk to take.
Sponsorships are definitely the highest if a youtuber actively engages in them, ad revenue vs patreon depends highly on if you have i.e. a small but highly active fanbase of core fans, versus a wider more general audience that you entertain a bit.
I think people should be more aware of the perverse incentive of YouTubers saying, "my guaranteed source of income is very little and unstable guys, I need you to also subscribe to my patreon" where - could YouTubers perhaps have a reason to act like their ad revenue is very little? In my experience, while ad revenue isn't great, for any decent-size YouTuber its still enough to live on and in any case it always stays a significant income stream.