Yes, the eSignature from DocuSign is currently the app already integrated with QuickBooks Online Advanced, tycalmc.

If you know other apps and want to use them, I recommend contacting our Intuit Developer Team. They can check and see if you can integrate it with QuickBooks. 

Here's how to get in touch with them:

1. Go to this link: https://developer.intuit.com/.
2. Scroll down, then click Contact us under the Intuit column.
3. Click Ask A Question.
4. Select your subscription.
5. Click Sign In and enter your QuickBooks Online log-in credentials.
6. Click Ask a Question again.
7. Enter your question and click Ask.

For other QuickBooks Online versions, we have the capture signatures function on the mobile app. It lets the customer sign with their fingers. I'm adding this article for more details and how to use it: Capture signatures using the QuickBooks Online app.

Let me know if there's anything else you need by commenting below. I'll be right here to provide the information that you need about adding signatures to checks.