Have there been any official book about this tribunal?
If yes, where there any special requirement for founding covenants or wandering magi?
I have some archmagus whom for some reason I haven't defined yet, fled the Transylvanian tribunal where the Tremere were a bit too much interested in his work and he felt no more safe, and I have located him in the Levant. But I want to be sure there are not so much rules against covenants with one magus or rules for wandering magi (He has a magical regio laboratory in some kind of ruins in the desert, but he is alone with his familiar, with no mundane or sodalis).
And that book's pretty fantastic. The sahir information and bits of the material are superceded in Cradle and Crescent, but also, there were also several articles in Sub Rosa 9 about the area, one by Sand and Blood's author.
Keep in mind that blood and sand is also out of date, being 4e. In particular, the tribunal of BaS stretches across mesopotamia whereas the 5e one is limited to the crusading kingdoms. Regardless, I don't recall limitations on new covenants, although there are only a few ones.
Probably the main point of interest to the hermetic landscape is that the covenants in Levant fall into three main camps: those pro-crusaders, those pro-arabic and those who would rather the Order not get involved.
So while ostensibly all part of the same Order, there's enough infighting within the ranks of the Hermetic magi that they don't even need a Saracen magical order to threaten the stability of the tribunal.
That, and the easternmost covenant in the tribunal is in Baghdad.
It's a partial guide to converting the ArM4 Tribunal into ArM5.
You will need a copy of ArM4 Blood & Sand to find this of use, although the first chapter is available as a free PDF.
It's not complete yet, but gives a rough idea on conversion of the basic concepts in light of the changes we introduced in The Cradle and the Crescent, which I see from another post about sahirs that you have purchased. I really haven't had a chance to convert the gazetteer section yet, but I do have a fair bit of developed material - it's unlikely that the Levant will be updated to ArM5 any time soon, so this may the closest you get to an updated treatment.
In direct answer to your question about the archmagus, the Levant is effectively the "Wild West" of Hermetic society and even in ArM4 there were no restrictions on founding covenants - you could perhaps even found a covenant located geographically in the Levant but belonging to another Tribunal (Normandy, Provencal, Roman) etc if you met the parent Tribunal's requirements, an idea hinted at previously and that I'll hopefully be exploring sometime.