Tunisia has three mobile operators: Tunisie Telecom (the state incumbent), Ooredoo Tunisia, and Orange Tunisia. All three operate 4G LTE networks. HelloRoam eSIMs connect via partner networks in Tunisia.
4G coverage is solid in Tunis, Sfax, Sousse, Monastir, Hammamet, and all coastal cities. The A1 highway corridor from Tunis toward Sousse and Sfax is well covered. Beach resort areas at Hammamet and Djerba Island have strong 4G throughout.
The interior of Tunisia and the Saharan south have lighter coverage. Kairouan, one of Islam's holiest cities, has 4G in the medina area. Tozeur and Douz, the desert gateway towns, have 4G in their centers. The Chott el-Djerid salt lake road has coverage near towns with drops in the open salt flats. The Tataouine region, known for Star Wars filming locations and ksour (fortified granaries), has 3G to 4G in towns.
The Saharan areas beyond Douz and east into the sand dune fields have very limited signal. Download offline maps of any desert route before departing from Douz or Tozeur.