Recently I've seen couple of issues with the user data that I get from Google Analytics related to Iframe's. I have web application hosted on domain example.com. I get different requests based on user needs like example.com/?id=1. In one specific case, my webpage is in an Iframe on another domain called iframedomain.com/example. When I check user data on Google Analytics, the user data I get from Iframe does not match what I see in HTTP requests to that specific page.
What I wonder is whether GA4 tracks users from other domain that has my Iframe in it or not? I have found some documentation on Cross Domain Measurement and Linker for analytics. I wonder whether there is another solution without exchanging client ID's or not?