For just about anything you want the alt-right has their "free speech" alternatives. The thing they are whining about is that the reach of these alternatives is way, WAY lower than the reach of the companies/projects of the alt-right. Almost as if the free market actually works and people deliberately choose to not engage in platforms dominated by alt-right hate mongers...
I think it's completely possible for a popular pro free speech platform to exist provided it is able to be more user friendly or have some other killer feature.