They offer wifi through an account with AT&T no one else seems to know what that is. There isn't a visible port for a sim card and none is mentioned at least not in my cursory reading of manual, but I am sure there is one somewhere.
The EmptyShelvesBiden administration is trying to sneak a universal kill switch into automobile requirements but I suspect there is already one built in whether available to users or not.
I may go to AT&T and see what I can find out, might be interesting. I have an iPad that I use as a mobile hot spot but not really the same thing. I have a Toyota App on the iPad and the wife's iPhone which controls all those functions but not a kill switch that I can find, maybe another App to buy for that function.
Everything going forward will have a continuing revenue stream, they need something to replace the service revenue they lost by making cars last so long, and they do last a long time for sure.
There are hardware solutions that include a telephone based modem and router for campers. You could probably make your own since you only need a telephone modem, which are available, and then you plug the modem into any off the shelf router. Many customers who don't have access to cable or DSL for internet use the telephone network for home internet access. Anyway, kind of cool network hardware is very modular.
Or like you said, you can use your phone as a wifi lan router (I think that they call it tethering) to your phone data network.