I’ve done some kernel development. I’d suggest using a modern system. Most of the basic stuff in the book is still accurate and there’s great documentation available to help find newer APIs. The kernel is always refactoring so learning to find newer info is part of the skills you’ll need to develop anyway.
That was a good read. I’d not really been sure of the differences between libadawaita and GTK were. It sounds like this frees up GTK to focus on being a cross platform GUI library, perhaps competing more directly with Qt. Meanwhile, libadawaita allows GNOME developers to keep leveraging GTK and tune it to their design guidelines.
I’ve only seen positive things come out of recent GNOME apps, but I wonder if the downside of GTK no longer embedding GNOME’s design language would be apps choosing to use GTK directly instead of libadawaita for better cross platform support. Will we end up with a less cohesive GNOME environment in the future?
For newer APIs the kernels documentation is good:
https://www.kernel.org/doc/html/latest/
As for getting help, the #kernelnewbies channel on the OFTC IRC network is a good place to ask questions.
Have fun learning!