I was going to say a similar thing. I'm still not sure I have seen an example of a browser at the scale of Firefox (hundreds of millions of users, 30 million lines of code) being successfully monetized, basically ever, unless it was entirely subsidized by a trillion dollar company that was turning its users into the product. Or alternatively, succeeding by selling off its users for telemetry or coasting off of Chromium and tying their destiny to Google.

All the "just monetize differently" comments are coming from a place of magical thinking that nobody has actually thought through. Donations are a feel good side hustle, but completely unprecedented for any but Wikipedia to raise money that's even the right order of magnitude. Any attempts at offering monetized services run into delusional and contradictory complaints from people who treat them to "focus on the browser" but also to branch out and monetize. Hank Green has used the term hedonic skepticism for the psychology of seeking to criticize for its entertainment value, which I think is a large part of what this is.

For a more serious answer on funding, I think the most interesting thing in this space is their VC fund. Mozilla has been brilliant in building up and carefully investing their nest egg from nearly two decades of search licensing, and while it's not Ycombinator, they have the beginnings of a VC fund that may be a very interesting kind of Third Way, so to speak, depending on how that goes.