Where did my audience come from?

Like everybody, we host a lot of content on landing pages.  Because we want to know who clicked on what content, behind each asset is a blind form submit.

I’m trying to run a report showing where people came from before they engaged with the first piece of content on any given landing page (social media, organic search, email sends etc.)   We use UTMs which update the ‘Lead Source - Most Recent’ field but of course, this field gets updated as contacts engage with more content.

I’m interested to learn how others have addressed my issue.

Any helpful hints or advice please?