Using classic Outlook for Windows in business environments
The registry change will start working after Outlook updates to build Version 2311 Build 16927.15000 and higher. Here is the Known Issue article for reference, Outlook blocks copying meetings with “Copying meetings is not supported.” - Microsoft Support.
Version 2311 is out to Current Channel and Monthly Enterprise Channel per Update History, Update history for Microsoft 365 Apps (listed by date) - Office release notes | Microsoft Learn. If you are on Semi Annual Channel and need the feature, you could switch Office to Current Channel.
If you want to switch to Current Channel, use the registry key in this article, Use a registry command to install Microsoft 365 Insider on Windows devices - Microsoft 365 Insider | Microsoft Learn.
- In Windows Search box search for Command prompt, right click Command Prompt and click Run as Administrator
- In the Command Prompt window paste this command and press Enter
reg add HKLM\Software\Policies\Microsoft\office\16.0\common\officeupdate /v updatebranch /t REG_SZ /d Current
- In Outlook click File, Office Account, Update Options, Update Now, to start to switch to CC and expect to restart Outlook to complete the update