some information appears to be missing in the online documentation for installation.
I installed root on Windows 10, with WSL running Ubuntu 18.04,
using precompiled binaries (pro 6.18/00) for Ubuntu 18 gcc 7.4
Despite installing all the prerequisites, I could get no graphics: indeed in the prerequisites listed for Ubuntu (at https://root.cern.ch/build-prerequisites#ubuntu) the required libtiff (actually libtiff-dev) is not listed (also libjpeg and libpng should be listed as libjpeg-dev and libpng-dev).
Moreover the link to the README/README on page
Hope this helps