I wonder if another path to “success” for ladybird could be rather than end users downloading it for the main browser, if it gains enough dev interest, we could get some kind of competitor to electron and it would end up getting bundled in that way as a lighter weight runtime to chromium for that use case.

Sure, it could easily take 1%.

Going above 5%, OTOH, I would be shocked to ever see happen, for two reasons. 1) Mass-market adoption requires working well on an enormous long tail, which is difficult without a large team. 2) The primary driver of playing at that size is mass marketing/distribution, which requires $$$. Engineering a great product is necessary, but not sufficient.

My perspective on this is informed by being on Google Chrome from inception to 2025. Chrome from near the beginning was well-engineered and had three compelling-according-to-user-research advantages over the IE of 2008 (speed, security, and not being made by Microsoft), but mass adoption depended on a large number of non-engineering factors, of which marketing/distribution was (to a then-mid-20s software engineer) the most surprising one. I didn't believe that was what made the difference in which browser most people used; I was very wrong. Techies are not the leading-edge trendsetters for the masses we sometimes believe we are.

IMO, taking mass market share in the future will require either a compelling-to-users product coupled with at least a couple hundred million dollars in marketing and distribution budget, or else something that is completely unlike web browsers of the past (maybe there's something that replaces the web entirely). No one has done the former since Chrome launched; the closest people have come to the latter thus far is things like Dia/Atlas that try to reimagine workflows in an AI context, and I think the market has not found those to be sufficiently different+compelling.