Hello @Achim and thank you!
If you mean going to Libya in your own car - I don't know if that is feasible. All the cars we used were Libyan. Both minibuses which took us from Djerba to Nalut and from Tripoli to Djerba and Toyota Landcruisers with which we travelled from Nalut to Sabha. The cars were logo-ed by Murcia Travel (
https://murcia.ly,
murcia.tr.ly@gmail.com) and I believe that company was the local collaborator of the Polish tour operator (Torre,
https://www.torre.pl). We also displayed Libyan flags on high antennas of the cars - not without a reason. What I am sure of is that free roaming around in Libya is out of question. Our documents were checked even a few times a day at road checkpoints and by patrols in the desert. Our official permit included the detailed itinerary. And for example we couldn't visit Kabaw, despite we were close and asked to do it, because it was not in the documents. The two policemen who accompanied us all the time (nice and friendly guys btw.) not only helped us with all the document checks but also took care that we followed the plan.
Re. Niger, I was there in November 2022. The planned route was as follows: Agadez, Timia, Assode, Arakao, through Tenere to Dirkou, then up to Djado and down to Bilma, and through Tenere back to Agadez. However, the military forbade us to cross Tenere, so we spent more time in Air, e.g. visited Iferouane, and went for 2 days to Erg Chiriet. The closed area and the reason for it were practically the same as now in Libya: the surroundings of the Salvador Pass are dangerous because of human and drug smugglers and bandits who make a living by robbing the illegal gold miners. Funnily, last year they managed to rob us anyway in Tibesti.
In Air we were escorted by 3 Toyotas full with Nigerien soldiers and in Tenere (Chiriet) by 6! That small army needed to be paid by the local tour company and indirectly by us. And that is, as far as I know, the issue with going there now. In theory travelling to northern Niger is possible and I know of at least one group which visited Bilma last autumn. But after the coup the cost of the military escort sky rocketed and the trip is not economically viable for the operators anymore.
If I can help in any other way, please let me know. Best regards!