Africa is out of any possibility. Only one or two branches of the whole T1a reached the Horn and Central Africa.
The two main possibilities are 1-Around Black Sea and 2- Around Caspian Sea. Between these two possibilites "Around Black Sea" is winning by far. But WHERE in the Black Sea is the big question.
Actually, we have ancient T1a1a-L208 samples deep in Europe between 7050-7600 yBP. The most ancient sample of 7600yBP found in the Danube carried around 35% Balkan HG atDNA.
7600yBP are just ~1000 years since the Birth of the main T1a1a-L208 branch T1a1a1-CTS11451. This means that both of the son branches belonging to T1a1a-L208 have been originated not too far from the Danube.
An example, the R1b-M269 carriers with ~1300 years (+300 years) of distance between them and their Steppe R1b-Z2103 brother found in Yamnaya, thinks this is enough to claim a "Kurgan origin". So, if they are wrong then we are less wrong and if they are right then we are more right.