Microsoft wants to retire the Search-Mailbox cmdlet from Exchange Online. But while the cmdlet available, it does a great job of removing mailbox items. If you get the search query right! In this example, we explain how to write a script to clear out calendar items from the mailboxes of multiple users.
https://office365itpros.com/2020/12/17/use-powershell-remove-exchange-online-mailbox-items/