Today's PSA: any cellphone in the US can call 911 in case of emergencies without a sim/esim, and without a carrier. Basically the cell modem will check for the best RSSI (or insert other fancy acronym here) tower connection and then use that carrier regardless of what service (or no service) you have.

So even if your phone is telling you there is no service, you have service...for calling 911 mostly.

RE GrapheneOS however, I'm not sure if when you deactivate your cell modem if that deactivates this feature? (Anyone know? #GrapheneOS kids?)

Also, re 911, you usually can text 911 as well. Please don't test this though...just mentioning this because the article linked references emergency calls. Not sure if that was the author's intention...if not, please ignore this lengthy spam post, I am a botnet.