The single biggest change since 1.5 is under the hood: MacSurf's JavaScript engine has been replaced. Duktape (ES5) is gone; MacSurf now runs macQJS which is a QuickJS port for Classic Mac OS and executes modern ES2023 JavaScript natively on Mac OS 9.
The most annoying bug I was able to fix that is also present up stream was this weird viewport, extra scroll bar, that would appear on some pages. I need to figure out how to get involved with the main repo if they'll have me.
Yeah, I wish more people contributed to Netsurf and it gets the momentum it needs to compete with Blink, Gecko and Webkit. So many divided efforts in this area - there's Ladybird, Flow, Servo, Goanna. Even just improving Webkit and making it truly multi-platform (it isn't available for Windows, and the Linux version is apparently not as performant) would greatly even the field.
Netsurf seems pretty closed in terms of who they allow to contribute. However, I need to look more into it and not use the excuse that it's "too complicated" to see if they are interested in my bug fixes.