This post provides everything you need to ensure Advanced Auditing is fully configured and auditing everything we possibly can for both existing and new users. I recently shared guidance for this via social media (see below), and it felt like a perfect time to revisit my previous posts and combine everything into one comprehensive guide :)
You likely aren't collecting all available events to the Unified Audit Log
First, not all events are enabled or retained optimally. Consider creating this policy in the Purview portal (leave users and record types blank to collect everything).
Retention is based on license... pic.twitter.com/IEKKfrkpI8