make a detailed description of installation of dumux on MacOS
There are three major os-platforms which users use mostly, one of them MacOS. With a few tweaks one can on all three be as productive develop DuMux as on Linux, at least if one has recent os-release. That's why the project should provide easy applicable descriptions for all three of them on the website and this not to deep hidden in it.
As far as I know one would install homebrew or shortly named brew there are packages from the MacOS-software selection tool (shop) and there are packages from macports. With brew easily install the necessary packages but it may also interfere with already selected tools.
I tried to document the possible package names on the DuMux wiki.
For the compiler toolchain, I see several options: Clang from the system, Clang from updated Xcode, GCC from brew (likely together with update Xcode), Clang from brew, or also clang or gcc from macports. Likely some ways are more preferable. So give hints. Provide if necessary an adapted cmake.opts of your solution to the user.