Is it possible to disable the possibility of signing on Portal for ArcGIS with ArcGIS account just like on ArcGIS Online in the SignIn options ? If not, is it scheduled at some point ?
I am using Portal for ArcGIS 10.3.1 but I did not find it 10.4 documentation as well.
Do you mean this?
I find that this JSON does not always work, and I simply navigate to the file and rename it to _OFF.html