The Messenger of Allah ﷺ used to give a single salam, facing forward.
حدثنا هشام بن عمار حدثنا عبد الملك بن محمد الصنعاني حدثنا زهير بن محمد عن هشام بن عروة عن أبيه
أن رسول الله ﷺ كان يسلم تسليمة واحدة تلقاء وجهه
Sourcing, its isnad is daif. Tirmidhi narrated it in the chapters on prayer, the chapter on the same subject, hadith 296, from Amr bin Abu Salama (the Syrian) from Zuhayr, by this chain, and said, Muhammad bin Ismail Bukhari said, "Zuhayr bin Muhammad, the people of Syria narrate munkar reports from him..." and so on, and Ahmad and others said the same. The hadith has corroborating narrations, but they are all daif.