The Samaritans are among the smallest religious communities in the world, numbering in the hundreds. They live in two places: Kiryat Luza, a village on Mount Gerizim above Nablus, and Holon, near Tel Aviv. The two halves of the community come together for festivals, above all for the Passover sacrifice on Gerizim, which is performed on the mountain and is the best known thing about them to outsiders.
They are not a remnant in the sense of a group whose institutions have lapsed. The community has a priesthood with a serving high priest, a liturgy, a calendar reckoned by its own priestly calculation, its own marriage and burial law, schools that teach the script and the reading tradition, and scribes who copy the Torah. The population is small enough that its size is reported as a specific number rather than an estimate, and it has grown over the last century from a low point that was genuinely precarious.
For the alphabet this is the single most important fact. Most of the scripts an atlas of this kind records are either in use by millions or in use by nobody. Samaritan is in continuous daily use by a few hundred people, which makes it one of the smallest living scripts on earth and puts it in a category with almost nothing else. It is taught to children as a matter of course. It is not reconstructed by scholars from inscriptions, and the people who write it are not informants about a tradition but the tradition itself.