Antitrust covers in general anticompetitive practices, and has done so since the original Sherman Antitrust Act. So, for example, colluding with another business to fix prices is covered under antitrust, even if the sum of the businesses concerned do not constitute a monopolistic power in the industry. The other common category is the various rules around the preference of a company's other product lines over competitors--the line between "legal" and "illegal" is a little more blurry here.
You can fall afoul of these conditions if you have "sufficient market power", which is a substantially broader claim than "monopoly power." I don't think there's any lawyer that would try to claim that Apple doesn't have "market power"--note that the smartphone market, from an OS perspective, is basically a duopoly.
You _might_ have an argument here: "The other common category is the various rules around the preference of a company's other product lines over competitors". We'll see what the courts decide
You can fall afoul of these conditions if you have "sufficient market power", which is a substantially broader claim than "monopoly power." I don't think there's any lawyer that would try to claim that Apple doesn't have "market power"--note that the smartphone market, from an OS perspective, is basically a duopoly.