gtk-sharp2-doc from home:Gankov project
Select Your Operating System
Add repository and install manually
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Gankov/15.5/home:Gankov.repo zypper refresh zypper install gtk-sharp2-doc
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Gankov/15.4/home:Gankov.repo zypper refresh zypper install gtk-sharp2-doc