Differentiate whether Paid / Organic / Direct / Referral

As of v3.0.36, there is new cookie called traffic_source

You can use this cookie to capture the source of the traffic weather paid, organic, direct or referral.

Paid: Traffic originated from Google or FB ads
Social: Traffic originated from Facebook, Twitter, Instagram, Snapchat, YouTube, Pinterest, LinkedIn, Tumblr organically.
Organic: Traffic originated from Google or Bing using the search
Direct: Traffic originated from bookmark or address bar directly.
Referral: All the other referalls not captured above
Other: Any other traffic not captured with the rules above.

In order to capture traffic_source information in your forms, you may have to add traffic_source as custom parameters in UTM. See How to add custom parameters?