DM26,
I use Turbotax Business (not home and business) to file partnership taxes. There is a form that requires a signature (8453-PE). Turbotax business allows users to print to pdf, sign, then scan or take a picture to upload. This procedure would work for the QBI safe harbor as well. There is no reason turbotax isn't able to do it beyond laziness, lack of competition, and incompetence.
