Info about their lobbying actions: https://sunlightfoundation.com/2013/04/15/tax-preparers-lobby-heavily-against-simple-filing/
Outside of tax preparers themselves, the industry is reinforced in its opposition to return-free filing by various trade and advocacy groups. One of these is the American Coalition for Taxpayer Rights (ACTR), an organization composed of various tax preparers and makers of tax software. In addition to Intuit, H&R Block and Jackson Hewitt, their membership includes TaxAct, TaxSlayer, Liberty Tax Services and more. It's a relatively new group, but in the only two years it's existed the ACTR has poured almost $450,000 into the tax lobby, including six mentions of opposing "simple-filing" in their disclosures.
So far from this old reddit mega-thread:
the most recommended over the services above is FreeTaxUSA
also there's this tip in the comments:
My tip: turbo tax only charges you at the very end when you go to actually file. So what I do is do my tax paperwork at both turbo tax and freetaxusa then compare the final return (or due) amount between the two. Every couple years, there’s a hundred or so dollar difference between the two and I dig in to find the difference before submitting and paying for ONLY freetaxusa
Edit: Credit Karma was another recommendation, but they are owned by Intuit since 2020:
en.wikipedia.org/wiki/Credit_Karma
Edit 2: Another article on industry lobbying