I'm surprised the article and comments haven't mentioned CreditKarma's tax solution yet, which is (actually) free. [1] Presumably their strategy is to take the users and data they get from offering free tax filing and use them to advertise lending products. I think that's a sustainable and politically feasible way to get free tax filing, actually; I expect that in ~5 years Credit Karma will have eaten a big part of TurboTax and H&R Block's lunch.
[1] https://www.creditkarma.com/tax