What is the apostasy of the recourse? And what is the ruling on one who seeks knowledge for the sake of Allah but desires fame when speaking?

There is no term "kufr al-ma'ab" (disbelief of the return) among scholars. Al-ma'ab refers to the return or resurrection. Learning knowledge for the sake of Allah contradicts the love of being seen by people out of pride. Whoever is like that is showing off to people, and this contradicts sincerity to Allah in seeking knowledge. It has been narrated in the Hadith: "Whoever learns knowledge to boast about it to scholars, or to argue with fools, or to turn people's faces towards him, Allah will admit him into Hell." However, if the original intention of seeking knowledge was for the sake of Allah, and then the intention of loving pride and showing off occurred, then there is a detailed explanation for that.