Do you want to use an existing C++ library in #Godot? Or maybe use #CMake instead of #scons for your C++ extension?
I created a #GDExtension template project to get you started:
https://github.com/asmaloney/GDExtensionTemplate
It takes care of all the setup/building/linking with godot-cpp/CI so you can focus on your code right away.
I look forward to any feedback!