What is the grammatical analysis (اعراب) of the hamza in "إلا إنهم ليأكلون الطعام" and why is it specifically broken (مكسورة) in this particular instance and not elsewhere in the Qur’an?

The hamza of "inna" (إنَّ) is

kasra (كسر) in the verse: (إِلَّا إِنَّهُمْ لَيَأْكُلُونَ الطَّعَامَ - but indeed, they will eat food) because of the lām (لَ) in its predicate, and it is also said because it occurs at the beginning of a sentence, similar to: "No emir came to us but that he honored me." Ibn al-Anbari mentioned two other reasons: the implied waw (و) indicating a state, or the implied "man" (مَنْ) before it. As for the fatḥa (فتح) of the hamza of "anna" (أنَّ) in Surat Bara'ah, it is because it is interpreted as a verbal noun (maṣdar) that is in the nominative case due to "preventing them" (manʿuhum).