Dad added my name to deed 4 years ago and passed away still living in the home.

My dad added me and my brother to the deed on his house in 2018 so that we could manage the property in the event that he was unable to. He passed in November 2021 and was still living in the house at the time of his death. We sold the house this week. Is the house considered a gift or inheritance? What are the tax liabilities? I intend to pay off my own mortgage with the proceeds of the sale. Is there a penalty or benefit for doing so?