Should the value of an Inherited IRA with no aftertax contributions be included in the total of all my traditional IRA's as of Dec 31, 2020 on form 8606 line 6?

No.   Inherited IRA's must be kept separate from your own IRA, unless it was inherited from a spouse and you had it transferred to your own IRA, then it is no longer inherited.

My question came up because I had a rmd from my inherited Ira as well as a non deductible contribution to my traditional IRA which had a basis.  I believe I answered  TurboTax incorrectly  on at least one of the interview questions ,which led to it calculating and showing incorrectly not all of the Ira distribution from the inherited Ira was taxable.  

Anyway after correction to the interview ,TurboTax no longer had any amount on form 8606 line 6 which resolved the issue and my questions .