In my country, with an admittedly quite simple tax code, the authorities used to publish each year official COBOL code that computed income tax.

They switched to Java in 2018-ish - and to Github instead of a random FTP server.

Doing your taxes has also been a no-op for many people the past decade or so. You don't do anything except read the tax report, unless you spot some mistakes or items missing in the report that was autofilled by the government, then you can go into the web form and submit the amendments necessary.