Bosnia and Herzegovina has three operators: BH Telecom (state-owned, serving the Federation entity), m:tel (serving Republika Srpska), and HT Eronet (a Croatian Telecom subsidiary serving the Herzegovina region). All three operators provide 4G LTE in their primary service areas and have some coverage overlap in larger cities.
Sarajevo has strong 4G coverage from BH Telecom throughout the old town (Baščaršija), Ilidža, and the airport area. Mostar has 4G across the historic center, the Stari Most bridge area, and the newer west bank. Banja Luka, the capital of Republika Srpska, is well covered by m:tel's 4G network. Tuzla, Zenica, and Trebinje have solid urban coverage.
Mountain areas and river canyon routes have weaker signal. The Via Dinarica hiking trail crosses remote terrain where coverage drops to 3G or nothing. Sutjeska National Park in the east has very limited mobile coverage. The Neretva River canyon south of Mostar has patchy signal on riverbanks. Download offline maps before any mountain or canyon hiking. Ski resort areas at Jahorina and Bjelasnica have reasonable coverage near lodges but may drop in backcountry terrain.