I just bought an official Pixel 9 to install GrapheneOS, and the process couldn't be simpler. Their webusb installer is extremely polished. You just plug your phone in, click through a few steps, and you're done. There's absolutely no reason to bother looking for a phone with GrapheneOS already preinstalled.

As a side note, I've been using it for a few months now, and it works great. All the apps I use run on it just fine. Battery life is great, and you don't have a bunch of cruft from Google running on your device. Can highly recommend for anybody looking for a phone you actually own.

This is not the related of preinstalled. Swappa is selling bootloader permanently locked forever phones as bootloader unlockable

As a note, swappa isn't selling phones with grapheneos preinstalled. It is selling used phones, you would still have to install gos.

I'm trying to go through Swappa to help reduce waste and save a bit of money. Unfortunately, when I decided to go second-hand, I didn't expect issues like this.