Will I have internet coverage on safari (e.g., in South Luangwa or Lower Zambezi)?

Yes, in key areas. This is the most important question. You will have reliable 4G/LTE coverage in the main towns (Lusaka, Livingstone, Ndola) and at the main gates and lodges of national parks like South Luangwa (Mfuwe area) and Lower Zambezi. However, once you are on a "game drive" deep in the bush, you must expect the signal to be intermittent or non-existent.