the operating system distributions (such as Parabola) that are endoresed by the FSF for following the Free Software Distribution Guidelines (see the 'dsfg' factoid)
separated between GNU systems listed on this web page: https://www.gnu.org/distros/free-distros.html and non-GNU systems listed on this web page: https://www.gnu.org/distros/free-non-gnu-distros.html
evaluated by the community on the 'gnu-libux-libre' mailing list - please do get involved if you are interested - the evaluation protocol and criteria, as well as the current status and results of the prospective distros currently in the queue can be seen on this web page: https://libreplanet.org/wiki/Incoming_distros