Open source team code review tools to work with a local git server?

Hello,

As the title suggests, my team and I are looking for a possibly open-source code review tool. All our code is committed to a local git server and we use GitExtensions as the GUI of choice.

We are firewalled and do not have access to the internet at work apart from a VMWare instance. We are looking for a team code review tool along the veins of Gerrit code review, but possibly one that doesn't require internet access to set up.

I'm new to software development and we don't have any experienced engineers on the team who have used a tool or similar, so I apologise if this is a noob question. I appreciate your time.