Taken from Mediavine:
GA4!!!! Learn what to do now and what to expect later
Google sent out this email to everyone still using Universal Analytics this week (or maybe everyone hard to say with Google), and so we have had a lot of questions, and I wanted to put together a few resources in one place.
If you have not set up Google Analytics 4 yet, we recommend that you do so ASAP. This article we put together last year is still accurate and super easy to follow.
The reason we recommend knocking this out ASAP is so that you can collect UA and GA4 data side by side through July when UA is deprecated.
BE CAREFUL TO FOLLOW THE INSTRUCTIONS AND NOT DOUBLE YOUR ANALYTICS
Doubled analytics installed on your site will cut your page RPM in half (NOT your money, just RPM -- basically it screws up the math), so you don't want to do that. If you use the help article and/or the wizard it just uses your existing site tags and it's really simple. I am a procrastinator and just did mine this morning to write all this up
DO NOT DELETE YOUR UNIVERSAL ANALYTICS!!!
Lots of !!! because this is important. Your Mediavine dashboard (and probably many other tools you use) still requires a Universal Analytics connection. It's how we calculate RPM, create ad unit health checks, pull in page level data and traffic by source, etc. That's why it's required in your contract.
Speaking of the Mediavine Dashboard
We've been getting lots of questions about when we will be able to connect the dashboard to GA4 (especially since Google is pushing it so aggressively ), and the answer is by the deadline! Our engineers are working hard, but there are lots of little details involved with a change this big, and because analytics provide us with so much important information, we are being EXTRA diligent.
WHAT ABOUT WEB STORIES ANALYTICS?
Our recommendation for Web Stories has always been to set up a separate Google Analytics Property to track Web Stories. Traffic to Web Stories is not the same as traffic to your site. If you have set up a separate property to track Web Stories, following these same instructions for that property is really simple.