This is the first time I'm using the Unitree Go2 Pro Robot Dog with the Smart Follow function out in my neighborhood. I just received the Go2 Pro and I'm trying out all of the features. If you are considering either the Air or Pro versions, this feature is the main feature that the "Pro" model offers. Here it is in action.
The feature involves clipping a small beacon/controller to your right hip. The dog follows that controller and orients itself in the same orientation as the beacon as well. To activate the Side Follow function you stand next to the dog and press the M button twice quickly (quite quickly). This will cause the dog to start marching. At first it took me a few tries to get it to enter side follow mode, then I realized that you have to push the button twice quite quickly.
The L2 button is supposed to turn on object avoidance, but my luck getting that to work hasn't been perfect. I'm getting better though. I hope to have it all figured out soon.
Using the joystick on the side follow beacon will control the dog but it will also turn off side follow mode. This will also allow the dog to stand still. Useful if your neighbors are walking past.