Samsung has apparently started testing a beta of for the with a small set of users in the U.S. The update appears to currently be targeting some Note 5 owners on AT&T, with testing pool said to be as small as 200 people.
The beta build number for this beta is MMB29K.N920AUCU2BPB1, and it weighs in at 1355.94MB. While Samsung has yet to offer a Marshmallow update to any of its devices, it has recently stepped up its efforts, for Marshmallow on the Galaxy S6.
Source:
