I never saw the Messenger of Allah ﷺ perform the forenoon prayer except when he returned from a journey, in which case he would pray two rakahs.
حدثنا معتمر قال سمعت خالدا عن عبد الله بن شقيق
ما رأيت رسول الله ﷺ يصل الضحى إلا أن يقدم من سفر فيصلي ركعتين
Its isnad is sahih. It is found in Bukhari, 3/10, no. 1128 (Fath), Muslim, 1/497, no. 718, Malik, 1/152, no. 29, and Bayhaqi, 3/49. Bukhari attributed it, but the meaning of the hadith is not that the Duha prayer is not a sunnah. It has indeed been established from many of the companions that they saw the Prophet pray Duha. This has come up many times before, or we have commented on it.