Some forms aren't available to be e-filed yet. This could be because the IRS and/or State hasn't released the form to be electronically filed. Once they do release it, it might take a few days for TurboTax to integrate it into the system.
If the form says it's Unsupported, it means that it is not supported by TurboTax, and you won't be able to file it electronically; instead you will have to print and mail either the form itself or the whole return.
Please refer to the link below for when this form will be ready to be printed, or e-filed.
When will my individual tax forms be available in TurboTax?