The UI isn't great* and if you do complex stock trading it can be a pain to add the necessary information, but for the vast majority of people it works just fine.
It also shows if it is better to use the standard deduction or the itemized deductions for your particular case and also calculates your effective tax rate.
In fact, the Java App has for years been the only way to file personal income federal* tax. The paper forms were abolished because (almost) no one used them and they had a large rate of mistakes.
* The Java desktop app runs on Linux, macOS and Windows. (And possibly others) * There is a separate mobile app but I haven't actually used it. * In macOS there was bug in last year's version: it used ctrl instead of command for things like copy and paste. * There is no state income tax in Brazil.