The men's football competition is always strange and unpredictable to me, because the squads are by definition suboptimal. I have no idea who will play in the Olympics, even if I regularly watch football.
Either way, France and Brazil seem inevitable with the level of talent available in their countries. I voted Mexico for the 3rd medal, because I wasn't particularly impressed with Germany and Spain in the recent U21 Euro's. I can imagine countries like Mexico and Japan will give higher priority to the Olympic squad, while Spanish and German eligible players such as Ansu Fati, Pedri, Havertz, Musiala, etc. might not be in their respective squads.