I am also trying to implement Google Analytics 4 on my store. Since I don't have Shopify Plus I can't edit checkout.liquid, so ideally we would have an update to the integrated Google Analytics feature in Online Store Preferences.
I contacted Shopify support a few days ago and am still waiting on a response. Ideally they would have rolled an integration out in tandem with GA4 -- especially since we're in Q4 now.
If you don't have Shopify Plus you can't edit checkout.liquid, meaning you can't track cart conversion statistics. That's why Shopify offers an integrated solution. But they haven't updated it in a long time it would seem. It's possible to fire the GA4 tag by adding it in the Additional Lines of Code under Google Analytics Settings in Online Store Preferences, but you can't take advantage of enhanced ecommerce tracking.