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One alternative is to subscribe to iCloud calendar with your Exchange/O365 email accounts or any Outlook account, and then sync the same accounts in Outlook for Mac. See details:
An error occurred while saving the commentGreg Mancuso commented
The "alternative is not an alternative - one way communication (at least one way the works consistently). And you have to share your iCloud calendar as PUBLIC!
Not going to happen. That is simply an insulting response by Microsoft.