It's a self-imposed ankle bracelet on steroids.

Metadata is a real problem. Those who sell it stay quiet, those who buy it and use it, don't want to reveal much. ADs weaponisation like Fog Reveal and recent starlink deanonymisation, is a problem. People should be aware that ADs and other metadata including telemetry is not nothing. I personally witnessed a person saying "but it's just my wifi network name" being sent. What people dont understand is the scale at which this is happening and this scale together with analytics, reveal a lot. People are not aware of data brokers who sell millions of such metadata records. Mercenary groups are for sure very interested in things like metadata from IoTs, for example knowing where the power was cut off is a huge advantage. I would even go a bit further - such mercenary groups could launch a legitimate IoT company and push cheap legitimate IoTs like lightbulbs to a local or glob market and then do an analysis of the metadata.

Graphene users disagree with you

If you have a cell connection, then you’re still giving up tons of data.

I know you’re just being snarky but I’m going to answer it like you were serious in case someone believes you. Graphene is best in class but it’s not magic. It’s software. It doesn’t stop cell network metadata, IMEI, WiFi emissions, device fingerprinting, location correlation, etc and GrapheneOS doesn’t claim to.

What’s the alternative? Or at least the best way to mitigate?

I don't

You're right. I was being snarky.