Can you bring your phone into the waiting room of a courthouse when you’re called for jury duty?

The rules vary. Some will permit them in the waiting area, others will not. When you get called for duty, you should receive a sheet of instructions with the rules you should follow for the day.

Not where I live

Yes, in the general waiting room, but once called to court, turn it off. You don't want the judge to take it away from you.

There are thousands of courthouses in the US and each has their own set of rules. I have sat in court cases many times and in the courts I visited the only requirements were that the phone be set to silent and no talking on the phone while the court was in session. I have heard of courts that will actually require you to turn the phone completely off as well.

No. That would be contrary to the rules in such places. You may even be prosecuted for contempt of court if you did so.

No you cannot, period