Login to the self-service portal with an M365 account that is a member of the DelegatedRestoreOperatorsForM365BackupPoweredByVeeam group.
US Portal: https://vbm-01.e01.us.sherweb.cloud
CA Portal: https://vbm-01.e01.ca.sherweb.cloud
Click on the word You to bring up the Specify Scope window.
Click on Filter to bring up filter options. Put a checkmark for User and uncheck any other options. Finally click Apply.
This will show a list of all users backed up by M365 backup powered by Veeam.
NOTE: If you wish to exclude any of these users from the backup jobs, that can be done in the Microsoft M365 portal by adding those users to the ExcludedUsersForM365BackupPoweredByVeeam group. Users added to that group will be excluded within the next five days.