Conclusion

Once these changes have been applied, we can see the request sent to Google in GTM's server-side preview. This request should no longer contain any personal information or user identifiers.

If this were the case, we could delete, anonymize or permanently pseudonymize these fields in the GA4 tag configuration, as we've just done.

How to view outgoing requests from sGTM to GA4 :

Preview > Select the event to be tested from the list on the left > Request (1st tab) > Outgoing HTTP Requests from Server > Select the request we're interested in > all the information sent to GA4 can be found on this page.