The only way I really see Algeria remaining "French" is if the French Union worked + survived. And that too, it would likely only be able to work as a truer confederation, rather than something under French supremacy.
A variation on this might be a French Union, along with the rest of N. Africa and the Levant being incorporated into a wider European-Mediterranean Community -- maybe instead of the OTL EU you get something like an inner core Western European Union and an outer tier that incorporates the Balkans, Turkey, the Levant, N. Africa, and the French possessions (including Algeria) into a wider block.
The problem is getting from most plausible post-1900 scenarios to something like this. Theoretically possible, but I don't know that anything like this really that plausible.