Thanks to all for answering. But in what concerns the Sea Control campaign, there only are 2 sides available (Egyptians & Persians), and both end in the same, premature fashion. I tried the campaign from the Persian side, a few minutes ago, and was not allowed to proceed beyond turn 1 : got that...

I purchased the game on 26 March. I did not have the patience to finish the Tutorial campaign, having already played other (somewhat) similar Slitherine games (Legion, Chariots, Spartan, Troy). I then preferred to dive right into the long "Sea Control" campaign, playing as Egypt. On turn 1...