On my 2023 1099, there is an amount indicated as "deemed premium". Is this amount taxable income? The heading says these items not reported to IRS.

No.  This "deemed premium" is for your informational purposes; it is not reported to the IRS as ax taxable amount.

Deemed Premium means the premium amount the Participant would have been required to pay on an annual after-tax basis to the Prior Policy during the Premium Period.

To be clear, the amount listed on the line "Other Receipts & Reconciliations-Deemed premium" in the section titled Reconciliations, Fees, Expenses and Expenditures on my Combined 1099 from my broker... has no tax impact and is not input anywhere in TurboTax, correct?

Correct.