GA4 tracking ID (ex: G-XXXXXXXXXX) is displayed on the donation box

This is because you have entered the GA4 tracking ID instead of the full tracking code in the Analytics Tracking Codes field. For instructions on how to obtain your full tracking code, please click the link: https://donorbox.zendesk.com/hc/en-us/articles/15832122040084-How-to-set-up-GA4-tracking-inside-the-donation-form.

In the Tracking tab of your campaign editor, please insert your full GA4 tracking code (not just the ID) into the Analytics tracking codes field of your campaign editor.

Make sure to modify the line gtag('config', 'G-XXXXXXXXXX'); to set the cookie flags as shown below. It is necessary for the tracking to work properly inside the embedded form (iframe)

gtag('config', 'xxxxxxxx', {
  cookie_flags: 'secure;samesite=none',
});