I say, and with God's success: Ibn Umar may Allah be pleased with him said: "I climbed above the roof of Hafsah's house for some of my needs, and I saw the Messenger of Allah ﷺ fulfilling his need while facing away from the Qiblah and facing the Levant," in Sahih Bukhari 1/68, and Sahih Muslim 1/224. Facing the Qiblah and turning away from it while fulfilling one's need is highly disliked, whether in the desert or in buildings; as reported by Bukhari in his Sahih, from Abu Ayyub Al-Ansari may Allah be pleased with him, who reported: "When you go to relieve yourselves, do not face the Qiblah nor turn your back to it, but rather face the east or the west." There is no distinction made between open spaces and houses, and acting upon the words of the Messenger of Allah ﷺ is preferable to acting upon the words of a companion. The narration of Ibn Umar may Allah be pleased with him can be understood as being in a state of necessity, or it may have been before the prohibition, or perhaps the Prophet ﷺ had turned slightly away from the Qiblah, such that the matter was not clear to Ibn Umar. Refer to: Bada'i Al-Sana'i, 5/126, and Tabyin Al-Haqaiq, 1/166, and Fath Al-Qadir, 1/419, and Allah knows best.