Forms 8986 and 8978 are not supported by TurboTax. See page 2 of this IRS document for next steps: Instructions for Form 8986, Partner's Share of Adjustment(s) to Partnership-Related Item(s)
The form you need to file is discussed here: About Form 8978, Partner’s Additional Reporting Year Tax
why doesn't TurboTax support Form 8986 since it seems somewhat common?
I too recently received a Form 8986 for two years (2021 and 2022). It was confusing and some entries look contradictory to the original K-1s. I had to get assistance from a CPA to understand the forms. The CPA gave me some guidance and I basically understand the process. My 8986 only involves increases to investment losses, so my tax obligation would not increase.
A problem I see with the IRS instructions is it doesn't give clear guidance on how to file the Form 8978 and Schedule A. The instructions have you figuring out the tax on additional income, if applicable. How does the tax payer include that on their 1040 completed with TurboTax? The instructions tell you to "Report the additional tax on the "appropriate lines" of the reporting years return. Ok, so what is the appropriate line?
I may call the IRS to see if they can give further details, but I'm not very confident they will have an answer. Regardless, that will have to be an amended return.