Graphner As far as I know, if you insert a SIM card the first time you turn it on, the phone automatically contacts Google and the operator, creating a permanent footprint: registering the IMEI, number, phone model, region... I suppose these things will also be registered with GrapheneOS, but the point is to get Google to suck up as little as possible or nothing at all. So my idea is to never connect the phone with the Android that comes with it and only use the SIM card once I've installed GrapheneOS.
A new phone connects to cell towers at the first boot, even without a SIM card. The only way to prevent connections to the cellular network is to enable airplane mode, when can only be done after the first boot. When GrapheneOS is installed on a phone, it will also connect to the cellular network after the first boot. After the GrapheneOS first boot, airplane mode can be enabled to prevent those connections.
When these cellular connections are made, the IMEI of your phone is associated with the physical location of the phone. You should assume the location where you perform the installation will be associated with the phone's identifiers. You should also assume the retail location where a phone is purchased will be associated with the phone's identifiers.
From https://grapheneos.org/faq#cellular-tracking:
Airplane mode is the only way to avoid the cellular network tracking your device and works correctly on the devices we support.
K8y The idea being if downloading gos on public wifi using your vpn, your vpn still has your data and knows you downloaded gos at xyz location and time...
Even if you're using a VPN provider that cannot be trusted, the provider would only know the IP address (and a non-precise location estimate) of the public Wi-Fi network. The VPN provider would have to work with the public Wi-Fi ISP to gather additional information. After the GrapheneOS installation image is downloaded, you can disconnect from the public Wi-Fi network and complete the installation in another location. Alternatively you could download the installation using Tor to avoid trusting a VPN provider.
Since you're interested in privately installing GrapheneOS, you should know that the device you are installing from may log and remotely store permanent identifiers from your new phone once the new phone is connected using USB. See https://discuss.grapheneos.org/d/9954-usb-traces-left-on-device-used-to-install-graphene-from and https://discuss.grapheneos.org/d/27314-privacy-risk-of-booting-on-an-idd-device. For an extremely private installation, both devices should be erased or factory reset after installation. Be aware that sharing USB or Bluetooth devices (headphones, chargers, and more) across the new phone and other devices may associate them together, possibly by third parties depending on your setup.
https://discuss.grapheneos.org/d/28401-how-can-i-setup-and-use-my-pixel-10-completely-anonymously is a good read.