I have some blog posts from the effort to write the new backends which gives some additional details.
https://blogs.gnome.org/chergert/2022/02/14/modernizing-gtks...
https://blogs.gnome.org/chergert/2020/12/15/gtk-4-got-a-new-...
https://blogs.gnome.org/chergert/2021/02/24/gtk-4-ngl-render...
I have some blog posts from the effort to write the new backends which gives some additional details.
https://blogs.gnome.org/chergert/2022/02/14/modernizing-gtks...
https://blogs.gnome.org/chergert/2020/12/15/gtk-4-got-a-new-...
https://blogs.gnome.org/chergert/2021/02/24/gtk-4-ngl-render...