How to people check in their modems to AMM

I just wanted to get an idea on how people do the initial check-in for their modems in. We currently have rv55 pro lte-a that check into AMM. Our AMM portal is in our Local ICS env and does not have direct internet access. We have a private cert that we put onto our modems and a base template that allows RV55 Pros to check into the AMM portal. The issue is this requires us to log into every device to add the cert and the base config as you have to push the buttons to do it (I have not really found a way for these modems to check-in automatically). This is a loaded question but is there a way to push the cert to the device and way for the modems to check in automatically to a local instance of AMM?