Thanks for voting!
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 commentGabriele commented
Thx for prioritizing the iCloud calendar & contacts synch. To be honest, I am a bit surprised that there are only workarounds available and no proper 'official' synch option. What is the value add for Outlook for Mac if you cannot synchronize iCloud directly?