@Opus 17 , the changes made by Section 604 of the SECURE 2.0 Act allows the employee to elect that employer contributions are to be made as Roth contributions, plan permitting:
https://www.irs.gov/newsroom/secure-2-point-0-act-changes-affect-how-businesses-complete-forms-w-2
Notice 2024-2 Q&A L-9 indicates that the contribution is to be treated as a regular traditional IRA contribution followed immediately by an in-plan Roth rollover (without regard to any after-tax amounts in the traditional 401(k) account that would otherwise trigger prorating of the taxable amount), so in combination with reporting the employer contribution with code R in box 13 of the Schedule K-1 (Form 1065), the plan should have issued (or will issue if Schedule K-1 is reportable on the 2024 tax return instead of the 2023 tax return due to the plan using a fiscal tax year) a code G Form 1099-R reporting the entire employer contribution as taxable.
This means that the reporting on the Schedule K-1 is correct and the partnership gets a deduction for the contribution. The employee pays the tax on this employer contribution.
