There is no "generally accepted value" here. Its contentious to say there is a natural limit at all.
Dunbar's number also has nothing to do with this type of society. The American Amish community (150k population) is basically an anti-modern religious group which is run on a communal model. Many members of that society live all their lives without meeting each other. As another commenter mentioned, Mondragon in Spain has close to 75k members in its cooperative.
The Amish are split up into smaller communities and establish new settlements when density gets too high. The Wikipedia page itself mentions that the Anabaptist Hutterites limit themselves to 150 person groups.
For communal arrangements like this, I think the generally accepted value is around 200. See "Dunbar's Number": https://en.wikipedia.org/wiki/Dunbar%27s_number