Eh, osx is its own thing at this point. The parts that really matter for a browser (UI/media, sandboxing, flipping page permissions from write to exec) are all osx specific.
“Linux” isn't one target, either. You have X11, Wayland, PulseAudio, JACK, Pipewire… That's just the more common userland windowing and audio APIs. (Yes, most of them have compatibility modes for others, but they don't quite work as well as not using the compatibility modes.)
