Otherwise, it's actually far more advanced than Wayland, and it had essential modern features implemented years ago, including HDR, VRR, and others.
Why hasn't it been ported to Linux? Probably NiH, probably it's Google's child.
What would be required to make surfaceflinger a practical Linux desktop compositor is merely some translation layer, equivalent to XWayland, that supports hardware acceleration. Such things have been written, but not open source and they never got traction.
The idea has been toyed with for over a decade: https://news.ycombinator.com/item?id=5317638
It runs on Android/Linux, not GNU/Linux. I would be surprised if there wasn't at least a bit of work needed to handle things like bionic vs glibc, and you'd really want it to act "normal" by being installed to FHS paths instead of Android's weird filesystem layout. All doable, I expect, but it would be a port.