Need help with MS Edge startup behavior

SMD-204 Welcome! First, all of the Microsoft Edge enterprise documentation can be found at aka.ms/deployedge.  There is a section called "Configure Microsoft Edge" which might be helpful to decide the best way to set up the browser.  

If you need the Microsoft Edge (Chromium) policy files, they can be downloaded here: https://www.microsoft.com/en-us/edge/business/download?form=MA13FJ

The corresponding policy documentation is here: Microsoft Edge Browser Policy Documentation | Microsoft Learn

If you decide to use policies, I think the best place to start is by taking a look at the HideFirstRunExperience policy.  The policy description also has some additional policies you might want to take a look at.  Here is the direct link: https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies#hidefirstrunexperience

-Kelly