Shopify merchants - as long as you are on Shopify Plus you can customize your Order Confirmation page.
Shown below are two different examples of companies who have added a field to their Order Confirmation page to collect Instagram handles and pass to their Gatsby account.
Example 2 is the easiest if you use Klaviyo, and I've included instructions below.
A custom Form connected to Gatsby via Google Tag Manager
Klaviyo embedded form connected to Gatsby via Klaviyo form integration
To facilitate this Example 2 integration, you will just want to start by logging into Klaviyo >> Signup Forms and selecting type: "embed"
At that point you can follow our standard Klaviyo form integration guide.
Choose this guide if you have our native Shopify App installed
Choose this guide for all our signup methods