gtk3 from home:Thaodan:GNOME project
Select Your Operating System
Add repository and install manually
For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Thaodan:GNOME/openSUSE_Tumbleweed/home:Thaodan:GNOME.repo zypper refresh zypper install gtk3