Wireless Joint

Based on your experience and requirements I think you have maxed out what you can reasonably expect using work arounds like consumer phone plans sims in routers. About the only thing I could suggest is you go to the business sections of the wireless company world and see what they might have for ...

First I need to say I am jealous, a RV lifestyle with +Cash Flow! :mrgreen:
There are two new units from NetGear that just came out or not out yet.

LBR20-Orbi LTE Tri-band WiFi Router
LTE Category 18
https://www.netgear.com/Orbi/LBR20.aspx


NIGHTHAWK® M5 MOBILE ROUTER (MR5200)
5G WiFi-6 Supports ...

If you like building things take a look here
WG1608V2 5G Ready Cellular Gigabit Router With Dual Band (2.4GHz-5.8GHz) WiFi

https://thewirelesshaven.com/shop/routers/lte-rou ... 8ghz-wifi/

Peplink makes some high end modems with Redundant SIM slots with automatic switching for reliable network.

https://www.peplink.com/products/max-si ... ent-router

https://www.mobilemusthave.com