I followed community article for entering a backdoor Roth, but the Turbo Tax system is still showing the conversion as taxable on my 1040. I have a decedent IRA as well.

If you have more than one Traditional IRA and some of the accounts have pre-tax money in them, then the pro-rata rule will apply when you convert Traditional IRA funds to a Roth IRA.  

Every distribution from a Traditional IRA is considered to be a mixture of the pre-tax and after-tax money in all of your Traditional IRA accounts.  Therefore, when all of your Traditional IRA accounts are considered, the distribution that was converted to the Roth IRA is made up of pre-tax and after-tax money and the pre-tax portion will be taxable when converted to the Roth IRA, even when the backdoor method has been followed.