Articles in the HOWTOs category
How to build an only-slightly-less-than-trivial GTK4 app using Flatpak
GTK4 is pretty new, and so it's likely that if you want to target it, you'll need to get your head around Flatpak in order to distribute your work. Here, I've taken the GTK4 'custom drawing' example from the GTK docs and wrapped it in a meson and Flatpak example, with a bit of explanation.
read.