Based on the info I found on the IRS website, you DO need to mail Form 8453 and include (see the box on the form to check) Form 8949 if it was not included in your e-filed return.
See the attached webpage from the IRS. The instructions include both Form 8453 and instructions on mailing your forms to the IRS. You need to do this within 3 days of having your return accepted by the IRS, so don't delay. You also may want to mail this via certified mail so that you have proof of receipt by the IRS.
2023 Form 8453 (irs.gov)
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
