Do you have reason to believe that the coastal countries with uplinks will not provide connectivity to their neighbouring countries?
They will surely have connections, but why would they provide transit? Is this a trickle-down theory of connectivity?
I believe many inland countries get their transit through neighbors. For example, I believe Rwanda gets ~99% of their data through Uganda/Kenya and Tanzania, and only a tiny bit goes through Satellite. I can't say for sure nothing goes out through the DRC or Uganda/South Sudan, but I'm pretty sure it's quite, quite small.
That is correct. Plus limited satellite uplinks. The undersea cable connectivity especially in East Aftica sucks. I have the feeling the primary reason why these cables exist is because they connect South Africa to the huge cables between Europe and East Asia.
I already know that they do not. This isn't the first subsea cable that goes around Africa.