brother mohammad ali hasan noted down jahalat of sheikh khamees, let me share his work alongwith some addition from my side as well
sheikh uthman khamees writes in moqadama in his book
“ahlusunnah did not name mahdi as montazir/awaited. and they are not waiting for him to complete religion for them. and this is opposite to what shias do”
[ متى يشرق نورك أيها المنتظر؟! ], page 17
well interestingly, we find ibn hajar makki writing in al-sawaiq-ul-mohariqqa

abu-ul-qasim al-hujjat

at the time of death of his father, his age was 5 years. but allah gave him wisdom even at this age. he is also called montazir/awaited. this is because he had gone missing while he was hiding in madina, and then none knew where he was…”

[barq-e-sauzan, urdu translation of al-sawaiq-ul-mohariq, translated by akhtar fathpuri, page 689,printed by shabeer brothers, lahore, pakistan]

apart from this, there are many scholars who have written books which included al-montazir in the title
let us see a few
1- ibn hajar haithmi wrote a book named
[ القَوْل الْمُخْتَصر فِي عَلَامَات الْمهْدي المنتظر ].
2- dr abdul azeem bastawi wrote a book named
[ المهدي المنتظر في ضوء الأحاديث والآثار الصحيحة ]
3- imam yousaf bin yahya moqadasi wrote a book named
[ عقد الدرر في أخبار المنتظر ]
4- sheikh abdul mohsin bin hamd wrote a book named
[ عقيدة أهل السنة والأثر في المهدي المنتظر ]
5- allama hamood wrote a book named
[ الاحتجاج بالأثر على من أنكر المهدي المنتظر]
6- ibn baaz wrote in his fatawa
[ المهدي المنتظر صحيح، وسوف يقع في آخر الزمان، قرب خروج الدجال ونزول عيسى عند اختلاف بين الناس ].
mahdi the waited/montazir is sahih. and he will come in end of times near the era of appearence of dajjal and coming of jesus when there will be difference in people
(فتاوى نور على الدرب لابن باز ، جمع د. محمد الشويعر ، ج4 ، ص 287 .)
you can read more about this issue over here