Can I e-file my federal tax extension even if I purchased/plan to file my taxes using TurboTax Desktop (not Online)? Also, when in March will it be available?

The form to request an extension usually becomes available in mid to late March---it is too early now.   An extension gives you extra time to prepare and file your return, but it does not give you extra time to pay.  You have to pay estimated tax due by April 15, 2024 even if you have an extension.

Thank you. To confirm, the form is available to file via paper on TurboTax Desktop but I was hoping to e-file through TurboTax Easy Extension and pay while filing for an extension. You are saying that the e-file through TurboTax would be available mid to late March?

Yes----the easy extension that you can e-file becomes available later in March.  We do not know an exact date.