Apache log search keywords are not listed in referrer
Solution 1:
This has nothing to do with Apache, and there is nothing you can change to get the search keywords.
Browsers are enhancing their privacy models by reducing information sent via the Referer header. This means that the default policy is to send only domain root URL in the Referer header on cross-domain requests.
The change has been implemented in Chrome 85.
https://developers.google.com/web/updates/2020/07/referrer-policy-new-chrome-default explains the changes in more detail.