You don't need software to file taxes. You can download the forms (1040, etc.) from the IRS website (and your state IRS's website), fill them in, print them out, and mail them to the IRS. It costs a few (literally a few) dollars for the postage and a certificate of mailing from the USPS as proof that you had the forms sent out by the deadline. The forms are not super straightforward but not incredibly complex either.…
To me, the value proposition of tax software is that it walks you through all the topics interview style, so you can kind of relax and go with its flow. Otherwise you've got to create that structure yourself - determining what's relevant, sorting income into categories, figuring out what boxes it's supposed to go in, what schedules you need, etc.
I wonder if libre software that only did the interview portion would be more sustainable. It could create category tallies and supporting statements that don't really change every year, and direct you to fill those numbers in on the forms in the appropriate box. Then it wouldn't have the maintenance burden of creating print-ready forms that haven't even been released until taxes are due.