This is the ultimate question, isn't it? What good is free content if it's not content you want to watch? According to the ATSC, currently 76% of US households have access to NextGen TV broadcasts. That includes the "broadcasters" of yore (namely ABC, CBS, Fox, NBC and PBS).
Not every station in every region will have converted to NextGen, though the rollout has been going on for eyars, so there are significantly more channels now than a few years ago. Also, conveniently, if you have the antenna and tuner you should be able to get all the "ATSC 1.0" (aka old-school HDTV) broadcasts. So you should be able to get all the major broadcasters for free over the air one way or another.
In many areas, however, you'll be able to get much more than just those. Most stations run multiple sub-channels, which in turn run different programming under the same "channel" banner. Plus, there are smaller broadcasters with varied content. For instance, I live in Los Angeles and there are nearly 200 channels broadcasting. Even smaller markets, such as Des Moines, Iowa, have nearly 100. Are all of these pristine HD and showing hours of amazing content? No, but it's all free.
While you won't be able to watch streaming shows like Arcane or The Last of Us over the air, you will find shows like Chicago Fire, NCIS, Grey's Anatomy and most major sports.