Snowplow JavaScript Tracker v3 can now be deployed directly with Google Tag Manager via a Custom Template. This is available in the Tag Manager Template Gallery.
There are two templates that you will need to use when setting up the Template for JavaScript Tracker v3.
Snowplow Analytics Variable Template: A variable template which can be used to easily apply a set of tracker configuration parameters to tags created with the Snowplow Analytics tag template.
Snowplow Analytics Tag Template: Load, configure, and deploy the Snowplow JavaScript tracker library. It supports the full functionality of the JavaScript SDK.