Yes, you will still need Form 8839 for the Adoption Credit in 2021 if you have a credit remaining from prior years. The adoption credit carries forward for five years if it is not used in its entirety.
You may need to verify the information that has carried forward if you filed with TurboTax in prior years, but if the adoption was finalized in 2020 and you did not have any new adoption expenses in 2021, then there should be nothing new to add.
