PS My apologies @nicktaylor, now that I've read more into Ladybird I see they're doing both. Creating a new browser and a new not-for-profit for it. I'll be intrigued to see how they plan to structure the org to avoid Mozilla's fate.
Also why they decided to start from scratch, instead of forking at least some components of a working libre browser. Even if only to swap them out over time, as Chromium did.