And by that I mean the mansas who are NOT mansa Musa or mansa Sundiata. Because every time I try to find info about Mali, it’s always those two.
Even D. T. Niane’s “General History of Africa” doesn’t dedicate more than one sentence to any mansa besides those two. Is there no oral history about them? Some kind of Arabic chronicle or something?
Unfortunately, there really isn't a large amount of English language sources on Malian kings. Really, there are only a few primary sources written at all about the Mansas.
Even Musa only receives a few mentions in Arabic sources, and very few are contemporary to his life. One which was was written by the Mamluk chancellor al-Umari, who most likely never met the king himself, but spoke with an Egyptian official who did.
Ibn Khaldun is our best source for the kings, but even his account is problematic at best - it's quite scarce on detail, and some historians argue that it's not even reliable at all, at least for Khaldun's characterization of the kings.
That said, there are a few useful sources - both primary and secondary - which may be worth looking into. With regards to oral histories, most exist in French (D.T. Niane's Recherches sur L'Empire du Mali au Moyen Ageis one example) or are otherwise difficult to find.
The preeminent author on medieval Mali is still Nehemiah Levtzion, and he has two books worth considering: Ancient Ghana and Mali) and the sourcebook Corpus of Arabic Sources for West African History). Both in English, and both have decent breakdowns for the history of the region, with one chapter in particular being dedicated to the kings themselves - though this is mostly a summary of Ibn Khaldun's chronology with supplemental information.
Finally, possibly the most colorful source for one particular king would come from Ibn Battutah, who traveled to Mali during the reign of Musa's brother, Mansa Suleyman.
Here are a few relevant articles - access is contingent on a JSTOR subscription of course, but in case they prove useful:
Levtzion: 13th/14th Century Kings of Mali (Basically the same info as his book chapter)
Ralph Austen, Jan Jansen: History, Oral Transmission, and Structure in Ibn Khaldun's Chronology of Mali Rulers
Nawal Marcos Bell: The Age of Mansa Musa of Mali: Problems in Succession and Chronology
(I'm aware this is about Musa, but it illustrates the issues with our primary sources and includes info on his successors Maghan and Suleyman)