Currently, there is no audit for any change made to the Environment Settings in Power Platform Admin Center. So, when there is an unknown change in a setting such as 'Audit settings' for the log retention policy for an environment, we have no clue to who changed it.

All current audit features are for changes inside the environment Dataverse and access to environment. Even Azure Purview.

I'd be great if we can have an audit to record change for general Settings in Power Platform Admin Center as well.