Ideally, you support potential candidates and existing representatives who will push public policy to enable the IRS (with help from the US Digital Service and 18F) to provide for tax filing directly to US taxpayers. This is the Path To Assured Success (public policy enabling and funding the IRS to directly support tax filing).
I can't imagine anyone having the will and resources to write their own tax prep system and then providing ongoing support for it though. Gonna take deep pockets and someone who really hates the professional tax prep market. It isn't a weekend project. This is a long, thankless grind.
https://www.warren.senate.gov/newsroom/press-releases/senato... (Senator Warren Leads Colleagues in Reintroducing Legislation to Simplify and Decrease the Costs of Tax Preparation and Filing)
These are the people you help get the bill passed:
> United States Senators Elizabeth Warren (D-Mass.) along with Senators Jeanne Shaheen (D-N.H.), Sheldon Whitehouse (D-R.I.), Tammy Baldwin (D-Wis.), Bernie Sanders (I-Vt.), Tom Udall (D-N.M.), Edward J. Markey (D-Mass.), Tammy Duckworth (D-Ill.), Maggie Hassan (D-N.H.), Jeff Merkley (D-Ore.), Cory Booker (D-N.J.), and Richard Blumenthal (D-Conn.) today reintroduced the Tax Filing Simplification Act to ease the tax filing process for millions of American taxpayers and reduce their costs. Last tax season, American taxpayers spent an average of 11 hours and around $200 preparing their tax returns -- a cost equal to almost 10 percent of the average federal tax refund. Representative Brad Sherman (D-Calif.) is reintroducing a House companion along with Representatives Eleanor Holmes Norton (D-D.C.), Don Beyer (D-Va.), Jamie Raskin (D-Md.), Tim Ryan (D-Ohio), Katie Hill (D-Calif.), Alexandria Ocasio-Cortez (D-N.Y.), Earl Blumenauer (D-Ore.), and Jackie Speier (D-Calif.).
Please call your representative and ask them to support this legislation. That is their job; to support the legislation you want enacted. It will take you at most ~15 minutes, and every call is tallied by congressional assistants.
https://www.commoncause.org/find-your-representative/