The Mac version has been around for years. All versions of TurboTax use the same underlying calculation engine, so it seems quite unlikely that there could be a broken link in the Mac version that is not present in the Windows version. As I said, a missing entry for Form 8606 line 6 would result in a taxable amount that is too low, not too high, so your observations are not consistent with a broken link to line 6 of Form 8606.
Perhaps the IRA Information Worksheet has lost your basis in nondeductible traditional IRA contributions and because of that TurboTax sees no need for Form 8606, resulting in the entire traditional IRA distribution or Roth conversion being taxable. It's all too easy to cause TurboTax to silently delete your basis by inadvertently answering No when TurboTax asks if you made nondeductible traditional IRA contributions. If you actually have no basis in nondeductible traditional IRA contributions carried in from line 14 of your 2022 Form 8606, the only way that you would have basis in 2023 is if you made and entered a nondeductible traditional IRA contribution for 2023.
Also make sure that you did not fail to mark the IRA/SEP/SIMPLE box on the TurboTax's 1099-R form that reports the distribution from the traditional IRA.
