DND from Desk phones or Can Admins set this for users

Yes, you can write an app, login with the super admin user, then you can read all users' presence status and set their status as well. Here is some code snippet in Node JS.

var SDK = require('ringcentral')

RINGCENTRAL_CLIENTID = 'your app client id'
RINGCENTRAL_CLIENTSECRET = 'your app client secret'
RINGCENTRAL_SERVER = 'https://platform.devtest.ringcentral.com'

RINGCENTRAL_USERNAME = 'super admin user name'
RINGCENTRAL_PASSWORD = 'password'
RINGCENTRAL_EXTENSION = '101'

var rcsdk = new SDK({
      server: RINGCENTRAL_SERVER,
      appKey: RINGCENTRAL_CLIENTID,
      appSecret: RINGCENTRAL_CLIENTSECRET
  });
var platform = rcsdk.platform();
platform.login({
      username: RINGCENTRAL_USERNAME,
      password: RINGCENTRAL_PASSWORD,
      extension: RINGCENTRAL_EXTENSION
      })
      .then(function(resp) {
          get_users_presence()
      });

function get_users_presence(){
    platform.get('/account/~/presence')
        .then(function (resp) {
          var jsonObj = resp.json()
          for (var record of jsonObj.records){
            console.log("====")
            console.log(JSON.stringify(record))
            // check the extension you want to change its presence status
            if (record.extension.id == "244609004"){
              set_user_presence(record.extension.id)
              break
            }
          }
        })
        .catch(function(e){
          console.log(e.message)
        });
}

function set_user_presence(extId){
    var endpoint = '/account/~/extension/'+ extId +'/presence'
    platform.put(endpoint, {
              dndStatus: "DoNotAcceptAnyCalls"
        })
        .then(function (resp) {
          var jsonObj = resp.json()
          console.log(resp.text())
        })
        .catch(function(e){
          console.log(e.message)
        });
}