Which verses are to be recited in the one-rak'ah Witr prayer: is it Surat "Sabbih Isma Rabbika al-A'la", or Surat "al-Ikhlas", or Surat "al-Kafirun", or all three Surahs?

The Sunnah for someone performing three Rak'ahs of Witr is to recite, after Al-Fatiha, "Sabbiḥ isma rabbika al-aʿlā" (Glorify the name of your Lord, the Most High) in the first Rak'ah, "Qul yā ayyuhā al-kāfirūn" (Say, "O disbelievers") in the second, and "Qul huwa Allāhu aḥad" (Say, "He is Allah, [who is] One") in the third. This is what the Prophet, peace and blessings be upon him, did. Some imams have recommended reciting Al-Mu'awwidhatayn (the two protective surahs, Al-Falaq and An-Nas) after Surat Al-Ikhlas in the third Rak'ah, while others have weakened the hadith reported regarding that. As for performing Witr with one Rak'ah, one may recite whatever they wish after Al-Fatiha, as no specific Sunnah has been reported for that. If one recites "Qul huwa Allāhu aḥad," there is no harm in it.