I think the solution is quite simple: add a silent argument to the GroupChatManager class. I think the only place that prints out to the console is in:
https://github.com/microsoft/autogen/blob/main/autogen/agentchat/groupchat.py#L388
and
https://github.com/microsoft/autogen/blob/main/autogen/agentchat/groupchat.py#L437

@ekzhu Can you please specify how exactly one should add the silent argument?

I tried adding a silent=True parameter when initiating the GroupChatManager class, but I got a TypeError that silent is not a valid input for a ConversableAgent (since the parameter is passed on to this class). Thanks for your help!

I think in this case silent should be GroupChatManager's own argument, as ConversableAgent doesn't have this argument.

silent is a parameter of send

I have a PR, but its not working properly. I gave GroupChatManager a silent option and I pass it to send, but the messages are never silenced. Can I get some feedback on this:
#2212 @sonichi @ekzhu