No Banu Hilal migration to the Maghreb is a good start.
This.
Without the Banu Hilal, I suspect the Berber language retains a much greater hold on the region, and Arabic is lessened.
That means the Maghreb countries become more like Iran or Turkey - countries which are still Islamic, but which have their own distinctive languages and cultures.
The next step might be to imagine that the Maghreb countries become Shia instead of Sunni. This might have some interesting and unpredictable historical effects.
Notably, the reason the Banu Hilal were sent west in the first place was because the Maghreb abandoned the Shia faith and turned to Sunni belief, which the Shia Fatimid dynasty in Egypt was unhappy about and decided to punish them.
The Shia faith has some interesting and esoteric branches, including a strong element of Neo-Platonist philosophy. This is particularly marked in the Ismaili sect of Shia Islam. This is the same branch which produced some fascinating offshoots, including perhaps the most famous of all - the deadly Nizari sect, also known as "the Assassins".
There are a world of possibilities, and one can imagine all sorts of unusual and esoteric religious sects evolving within the Shia branch of Islam. An alternative might be that some kind of Sufi belief system emerges in the Maghreb, perhaps under a charismatic teacher, eroding further the influence of the traditional ulemma. A figure such as al Hallaj, or some other spiritual leader, might do nicely.
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