Last time I tried this I bought two modems that should've worked (and did directly connected to a Windows PC) but they didn't when connected to a RT-AC86. Now I have a GT-AX11000 that I want a cellular backup on. What modems are good candidates for Tmobile US? (I've tried a retired Pixel 3 and the USB tether dies after sitting idle. I'm guessing that is a feature of newer Androids because my Nexus 6 would stay connected forever.)
Thanks! Unfortunately only two of the US models listed are 4G (3G is no longer active here) and it is questionable if they can be unlocked for use with MVNOs. I did figure out how to keep the tethering active on the Pixel 3 so that will be my solution. It involved enabling the Developer Mode settings menu and from there setting the Default USB Mode to Tethering.
On a related note, any idea why the GT-AX11000 doesn't recognize Surface Duo when it has tethering enabled? I can tether the Duo directly to my laptop, but when connected to the router it disappears (No Device on the port on the Network Map page) when I turn on tethering on the Duo. My best guess is that Microsoft is using a more Windows friendly tethering implementation.
After certain updates my REVVL V+ 5G started acting buggy. *Eventually I swapped it with an iPhone and plugged the REVVL into the USB 2 port of my AXE16000. *Just like you around 12 hours later the tether dropped. *Already a developer I tried changing the default USB mode to tethering. *It no longer drops. *Thank you for sharing this!