As you mentioned, it's probably best way to check the auditing logs for report/dashboard in settings via Admin Portal. Important, you need to be a Global Admin, within O365 or Azure AD, or at least have been assigned to the Power BI service administrator role.
Alternatively, you can use the Usage metrics functionality of Power BI service. Usage metrics captures usage information from all users, regardless of the license they're assigned (of course, Power BI Pro is a need!).
In order to see the Usage metrics, please follow the steps:
1. Log in to the Power BI service2. Navigate to the workspace your dashboards/report is located3. Look for the Usage metrics icon and click on it (below)
Above screen shoots come from the Microsoft Power BI documentation, where you can find more details: Usage metrics for dashboards and reports - Power BI
Hope it helps,