For the Recent Activity widget on the homepage of my community, can I customize this so when I click “see more” it goes to a new page? I'd like to have a unique URL for recent activity so that I can grab this URL for email marketing purposes. I am using a custom Zendesk theme (Indigo).

Currently, the Recent Activity widget in Zendesk does not support configuring a unique URL for the "See more" link out-of-the-box. By default, "See more" directs users to a standard activity stream within the community, and this URL is not customizable through the Zendesk Guide interface alone.
However, since you are using a custom theme, you do have the flexibility to customize your theme’s code to achieve this functionality however, I'm afraid that is already outside of our support scope. If you need help implementing these customizations, we recommend engaging a developer familiar with Zendesk theme customization.