My only wages are from a non-qualified deferred compensation plan. May I make a Traditional IRA contribution from this income? TurboTax for 2018 suggests that I can.

Pub 590-A informs that non-qualified deferred income is not included in compensation for determining the IRA contribution limit. So, it is possible that this is a bug in TurboTax, unless something has changed in the 2018 tax law.