> if a company makes a phone with GrapheneOS preinstalled, I'm giving them my money.

FWIW you can buy a Pixel (new or 2nd hand) and install GrapheneOS via the Web https://grapheneos.org/install/web with nothing (genuinely nothing) installed on your computer and get it working in ~15min (depending on your connection to download the ROM) out of which maybe ~2min will be your interacting with the setup process.

I initially bought an /e/OS precisely with your requirement, namely I "just" want a phone that works when I receive it, no tinkering, but having installed GrapheneOS myself few days (or weeks?) ago I can tell you, it's really straightforward.