Well, I'm using the Belkin PD Ethernet adapter with a 45W NekTech (USB-IF certified) at home connected to my Dream Machine.

https://www.amazon.com/dp/B086SV2FK4

https://www.amazon.com/dp/B0719KV9PH

Works fine. Ethernet is Ethernet.

Only issue is that it has to be connected AFTER the M2000 is completely booted.

Other then not needing to time when the adapter is connected I don't see a benefit to adding another router into the mix. Having to time it IS a valid concern, but it won't impact most people often enough to matter.

You mentioned using is as backup internet. In my area I cannot use T-Mobile as backup for Comcast because T-Mobile uses Comcast for tower backhaul. They both go down when there's an area wide outage. So I use AT&T or Comcast Connection Pro.