Add a teams-calendar to outlook
A channel calendar can be added to Outlook, but by default hidden. You need to use PowerShell to make this group calendar visible in outlook. This one will show events created in all channels of the team.
Please refer:
Connect to Exchange Powershell module and run the following command: Set-UnifiedGroup -Identity MyTeam -HiddenFromExchangeClientsEnabled:$False
An example guide here:
https://olafd.wordpress.com/2018/10/13/make-microsoft-teams-team-visible-in-outlook/
Official doc:
https://docs.microsoft.com/en-us/powershell/module/exchange/set-unifiedgroup?view=exchange-ps