If it is not funded through user donations, how is it self sufficient? Genuinely curious.

What would the checkmark mean?

Wikipedia is set up as a nonprofit. They have annual fundraising drives asking their users for money. They also have an endowment and receive grants.

A donation drive could be a good model but the decentralized nature of the platform would complicate things.

This is impressive despite my lack of understanding.

Yeah. I think this is pretty much the accepted narrative. Kill the 3P apps -> Consolidate the user base -> Serve everyone adds -> Hopefully turn a profit -> Go public or sell the company -> Founders/Investors cash out and profit.

The collateral damage is that they risk killing the culture that makes Reddit a place people want to congregate.