I just got [Test Setup #3] up and running last Friday (12/20/2019).
I’m using a Lenovo S145, booting ROOter OS off of a USB flash drive. I’m using an Amazon Basics USB 3.0 to GbE adapter in addition to the other parts.
Aside from creating the ROOter OS USB, no other configuration was needed to get the LTE up and running. This was by far the easiest to set up, and has been performing well.