Enablement of the module {dnf-module} warns about a conflict with postgresql:10 and ruby:2.5 as these modules are set to the default module versions on {EL} 8.
The module {dnf-module} has a dependency for the modules postgresql:12 and ruby:2.7 that will be enabled with the {dnf-module} module.
These warnings do not cause installation process failure, hence can be ignored safely.