Hi Jonathan, no tourist has done this route for years, far less using local lorries, even though, as you say, local transport continues across the desert. Tourists are not permitted afaik.
The fact that trucks are leaving in convoy (guarded?) suggests things are far from normal.

You will arrive in Algiers to change for Tam and they will say 'where is your escort?'
It is easier (or less difficult) to get a visa from an agency who will drive you around for at least €100 a day. Probably more as a single person.

Why are you going to IGZ - to get to Niger? You will have a visa?
Eventually someone will succeed in trying this, but right now it feels too soon.
You will be crossing busy drugs-arms-people-trafficking lanes to get to Agadez, a regional centre for people-trafficking.

Compared to adjacent places, the security situation was never bad in south Alg. (In Amenas attack was an anomaly - easily to pull off from lawless Libya.)
It's just that the very strict authorities don't want the hassle of conspicuous foreigners knocking about down there, and for some reason Tam wilaya (province) has been much more strict about this than Illizi wilaya to the east (Djanet, etc - open and more interesting for a visit, IMO).
Other recent posts mention things may be lightening up in Tam wilaya - but only for tightly controlled groups, I imagine.

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Morocco Overland 4 (2025) • Trans Morocco Trail