They actually do, there is alt-right Twitter aka gab.ai, alt-right Youtube aka Bitchute, alt-right Facebook aka Vkontakte, a boatload of "bulletproof" hosters and domain registrars. They even have their own TV stations (OAN, parts of Fox News), radios and podcasts.

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...