TurboTax does not support Form 8833 Treaty-Based Return Position Disclosure Under Section 6114 or 7701(b) .
You can prepare Form 1040 using TurboTax and print and prepare your Form 8833 separately to attach and mail.
You can amend your 2019, and 2018 returns. Your 2017 return can be amended - it must be received by the IRS no later that April 15 2021.
2018 and 2019 can be amended until 3 years from the original due date of their returns - April 15, 2022 and July 15, 2023. Treaty-Based Return Position Disclosure
