ISTM this really wants legislative action more than FTC action. “Price fixing with an app” should not be something probably illegal due to complex Sherman Act arguments that result in it taking years for the government to do anything about it. It should be directly an unambiguously illegal, with strong penalties (3x damages?) for both the companies using the apps and for the companies making the apps. And enforcement should be fast: the government should be able to entirely shut down these apps via a preliminary injunction.

And yes, maybe there should also be penalties applied personally to the executives who break these rules. But that’s a can of worms and it might be unnecessary.