Do I claim that I received the Stimulus 2 if it did not arrive until after December 31?

Yes, you will need to enter it as follows into TurboTax as outlined below.  This will ensure your Recovery Rebate Credit is calculated correctly.

To review your input in TurboTax, you will need to do the following:

1. In the Federal section, select Other Tax Situations interview section at the top of the screen.
2. Scroll down to the bottom and select Let's keep going. 

This will take you to the input section for the Recovery Rebate credit.

Be sure to indicate the actual amount of each stimulus payment you received on the page that asks if you received a stimulus payment.

There will be two boxes and both need to be completed.

See the following link for additional information on the credit and when it applies.

Recovery Rebate Credit eligibility