Can you actually recompile your kernel on Mac? And its functional?
I'll bet this isn't even the source code Apple uses, but rather they have a private fork with extra patches (similar to how Microsoft publishes OSS VS Code, but then uses their own proprietary version for releases).
You can, or at least could 5 years ago or so (and I bet you still could now).
However, it involved finding some random blog post on how to do it, and then even once I got it up and running there were some issues like the fans being pegged at 100%. Still, it was mostly functional.
I can speak to that via scuttlebutt from ex-apple friends. Apparently the intel power management code running in macos includes proprietary code from intel that they weren't comfortable opensourcing, for weird reasons.
Going forward, Apple won't officially support dual boot or alternative operating systems. Unofficially, they'll try their best to leave the options open for third parties like Asahi, but it will never be something they endorse as an option to macOS on their devices.
For example, there will not be an ARM version of Boot Camp published by Apple. If you want to run Windows on an Apple Silicon Mac, it'll likely be running virtualized under macOS or in an emulator under macOS.
If someone wants to write a bunch of drivers and hack a boot loader to get windows running natively - Apple won't stop them, but thats a heck of a lot of work.
Except Apple is also heavily going against Jailbreaking, with multiple lawsuits in the past, and system updates made specifically to patch them out, and nothing else.
Sure, you can stay on older iOS Versions, but you would be loosing actual improvements
https://github.com/apple/darwin-xnu