So, we use an Oracle database. If I wanted to connect to Oracle without Arcpy, I would use the python library Oracledb. Extra libraries, such as Oracledb, aren't really an option for us. We are sticking to what strictly comes with the python in Arc pro.
Anyways, I wanted to let you know that I actually had the GIS object intializing correctly when I uploaded it as a gp service. The issue was that I was trying to return the username from the GIS object and of course, as you mentioned, there was none so it threw an error when I attempted to return the username like so: gis.properties.user.username
Even though it wasn't able to get a username I was still able to get an item from the portal with the GIS object. The fault turned out to be my own. I'll see about registering the account running Arc Server with the portal, but I don't really see a need now since access to this gp service is managed by groups in portal.