flatpak from home:mkrwc:zigzag:15.3 project
Select Your Operating System
Add repository and install manually
For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mkrwc:zigzag:15.3/standard/home:mkrwc:zigzag:15.3.repo zypper refresh zypper install flatpak