Strange local happenings for sure. Not sure why you would be prompted to log into Google services unless it's a weird default option on your sim card when service is down. I know in my country there was an outage and I was prompted to log into something that I couldn't actually log into, not Google, but a similar behavior.
Purism won't be able to help you, they simply resell TMobile service, so if TMobile is down there's nothing they can do. Plus are known for terrible customer service and seem to be largely a scam. You may be able to ask for some compensation for the downtime but good luck!
You could get a backup Data SIM. Keepgo uses both TMobile and AT&T towers in the US. Not sure if they fall back or prefer one over the other. You can get an esim from them and only use it in emergencies.
Just an idea. But I don't think there's any conspiracy against non Google devices. Just wait it out, use Wifi, or change services.