I need the Mumble client for CentOS 8. In CentOS 8, Mumble is no longer included. CentOS 8 is based on Fedora 28. It is not possible to install the rpm file from Fedora in Centos8. Then I tried to build the package myself as an RPM, unfortunately without success. Mumble’s maintainer is John Popplewell (fedpop). How do I get his email address?
You will have to contact the CentOS community using their channels. It is based on Fedora releases, but it does not just use packages that were built for the Fedora releases. Fedora maintainers also do not necessarily maintain the packages in CentOS.