Sounds like a bug-- my 2026 R1T identifies chargers correctly (RAN sites show up as "adapter needed"; if I set the preferences to "no adapter" they disappear. The little elastic cargo net compartments in the Frunk are the perfect size to permanently store the CCS to NACS adapter so it's always ready
"I don't have any non-Tesla NACS vehicles to confirm, though."
Find a buddy with a non-Tesla NACS vehicle and try it out. You'll find the same thing the rest of the internet has found-- because it's going into a NACS vehicle the mobile charger tries to talk "enhanced J1772" rather than vanilla...
I've heard from others that the Tesla gen1/2 mobile charger will charge pretty much anything when it runs through a J1772 adapter... but if you're plugging into a NACS native vehicle it will just get confused and refuse
Just make sure it's a 3rd generation mobile connector, not the Gen 1 or Gen 2 mobile connectors-- they "speak" a Tesla-proprietary protocol, not NACS and won't work with a NACS Rivian vehicle.
If they're ordering a new R2, they don't need the universal wall connector. They should go with the standard Tesla NACS charger which is even cheaper, $450. That's what I use for my 2026 R1T and it works great.
They were in the wild for about a month while still available to order; first deliveries (in Seattle at least) were late December, and they were available to order through early February. But yeah, there's not very many out in the wild.
It was announced December 3rd; in Seattle the first deliveries were at the end of December (apparently somebody in Bothell got the first R1S Dec 27th, I got the R1T Dec 28th).