Ubuntu 22.04
sudo apt-get install libgtk-4-dev gtk-4-examples geany
Fedora 32
sudo dnf install gtk4-devel geany
openSUSE Leap 15.4 / Tumbleweed
sudo zypper install gtk4-devel geany
Source: Setup GTK4 Development Tools On Ubuntu, Fedora And OpenSUSE
#gtk4