UTM parameters: how to use them correctly and the 4 patterns that break GA4 channel grouping

I keep running into the same Meta-ads UTM setup at startups: utm_source=meta . Once Meta rebranded, this looks natural — except meta is not in GA4's official source list , so the campaign falls into Referral instead of Paid Social. The monthly report then shows "Paid Social dropped sharply" when really the classification just fell off. UTMs look fire-and-forget but they aren't. The moment you put a value GA4's classification logic doesn't recognize, the channel grouping is meaningless from that