Once you have both the cmake and the cmake3 package installed on your machine, you can use update-alternatives to switch between both packages.

Use the alternatives command to register both installations:

$ sudo alternatives --install /usr/local/bin/cmake cmake /usr/bin/cmake 10 \
--slave /usr/local/bin/ctest ctest /usr/bin/ctest \
--slave /usr/local/bin/cpack cpack /usr/bin/cpack \
--slave /usr/local/bin/ccmake ccmake /usr/bin/ccmake \
--family cmake

$ sudo alternatives --install /usr/local/bin/cmake cmake /usr/bin/cmake3 20 \
--slave /usr/local/bin/ctest ctest /usr/bin/ctest3 \
--slave /usr/local/bin/cpack cpack /usr/bin/cpack3 \
--slave /usr/local/bin/ccmake ccmake /usr/bin/ccmake3 \
--family cmake

After these two commands, cmake3 will be invoked by default, when you enter cmake from a bash prompt or start a bash script. The commands also take care of registering a few secondary commands like ctest which need to be switched along with cmake.

If you need to switch back to cmake 2.8 as the default, run the following command:

$ sudo alternatives --config cmake

There are 2 programs which provide 'cmake'.

  Selection    Command
-----------------------------------------------
   1           cmake (/usr/bin/cmake)
*+ 2           cmake (/usr/bin/cmake3)

Enter to keep the current selection[+], or type selection number: 1

The cmake: 3.11.4 version will still be listed when you run yum info because it is already installed, so disabling the AppStream repo won't affect what is shown. If you only want to show available packages (based on your enabled yum repos), you can run this instead:

yum --disablerepo=* --enablerepo=epel info cmake --available

If you want to install the latest version of CMake (or some other version), you can always download the binary distribution from the CMake download page.

Once downloaded, you can extract the package to somewhere you have access to on your machine, e.g.:

mkdir ~/cmake
tar xvzf ~/Downloads/cmake-3.18.2-Linux-x86_64.tar.gz -C ~/cmake

Finally, make sure you add the extracted bin directory to your PATH environment variable so you can run the cmake executable from the command line.