Hi everyone, I would like to ask if it is possible to prepare the agent so that it sends endpoint data to 2 different fleet servers that are not clustered

No, that is not possible. Osquery only supports logging to a single remote destination. What is your end goal? Maybe you can duplicate the logs in the logging pipeline?

I want to make it so that the fleet server present in our main office has visibility to all pcs and at the same time I have a fleet server in each branch office with visibility only of the pcs that are managed by that office. so I would need osquery to send data to both the main server and the server present at that secondary location

Is this motivated by wanting to give some users access to only the computers in their branch office? If that's the case, the Teams feature of Fleet Premium is designed exactly for that.