Alphie
My interpretation is that you are trying to identify ways of installing GrapheneOS that would minimize identifying information being sent by telemetry to Apple, Google, Microsoft.
(1) Use a router that supports installing a VPN configuration. Two excellent VPNs that support anonymous methods of purchase (cash sent through the mail or purchasing a voucher through amazon.com) are Mullvad and iVPN. After downloading the Wireguard configuration file to my phone, I changed the ".conf" extension to ".txt"; I then opened the file with a text editor (e.g., billthefarmer's Editor or Notes) and copied and pasted the content into my GL-iNet router.
(2) at a business with public wifi (such as a coffee cafe) activate the Pixel device and then use a laptop or another Pixel device with GrapheneOS installed on it to install GrapheneOS; that is what I did with an Apple laptop purchased at a b&m Apple store with cash and a Pixel phone purchased from Target with cash.
links:
https://www.gl-inet.com/solutions/vpn/
"GL.iNet routers support the following 30+ popular commercial OpenVPN and WireGuard VPN services. You can simply drag and drop your vpn files to activate the VPN function once you acquire the subscription of any of the below VPN service providers."
https://www.privacyguides.org/en/vpn/
https://www.ivpn.net/knowledgebase/billing/voucher-cards-faq/
https://mullvad.net/en/blog/2022/9/16/mullvads-physical-voucher-cards-are-now-available-in-11-countries-on-amazon
https://github.com/billthefarmer/editor
https://github.com/billthefarmer/notes