Whoever tells you that the Messenger of Allah ﷺ urinated while standing, do not believe them. He never urinated except while sitting.
أخبرنا علي بن حجر قال أنبأنا شريك عن المقدام بن شريح عن أبيه
من حدثكم أن رسول الله ﷺ بال قائما فلا تصدقوه ما كان يبول إلا جالسا
Graded hasan. Tirmidhi related it in the Book of Purification, the chapter on what has been said regarding the prohibition of urinating while standing, hadith (12), from Ali bin Hajar, with the same wording. Ibn Majah also related it in the Book of Purification, the chapter on urinating while sitting, hadith (307), through the hadith of Sharik the judge, with the same wording, and Israil and others followed him in narrating it (Sunan al-Kubra of Bayhaqi 1/101, 102). The hadith is also found in Sunan al-Kubra of Nasai, hadith (25).