There is a long thread on this same issue but under the subject:
Unable to efile due to QBI Deduction Worksheet Schedule B
TurboTax did in fact allow attachment of a signed Safe Harbor statement last year with the ability to e-file but it was a very late fix.
I would not recommend filing without the statement. In order to take the QBI deduction it has to be a qualified business activity which requires considerable, regular, and continuous activity. Rental activity generally does not qualify as such and has historically been deemed Passive income due to the lack of participation. The Safe harbor allows an exception to this.
This other thread has a lot more information.
