Should I enable the Ad Supported flag/label on Google Play?

Yes, Google Play considers surveys "ads" and therefore you should enable the "Ads" label for your app on Google Play Console.

You can follow these steps to complete the ads declaration:

1. Sign in to your Developer Console.

2. Select an app.

3. On the left side, select the Pricing & Distribution page.

4. Scroll down to the Ad Supported header, and fill out the ads declaration.