To get the ball rolling, Andretti had already signed a preliminary contract with Renault years ago. But that expired in March 2023. And at the moment, the French are showing no great desire to resume negotiations on a continuation. Renault, alias Alpine, does not want to get caught in the crossfire of a power struggle between the FIA and FOM.
If a team doesn’t have any contract with a PU supplier, they are assigned Pu with the least customers.
If Andretti enters in 2025 and don’t have a PU deal, Renault will be forced to supply them. If they enter in 2026 or later, there are three PUs with only one team: Renault (Alpine), Honda (Aston martin) and Audi (Sauber), so any of them could be forced to supply them.