quickduck The install steps requires extreme terminal work which I do not understand (I said I do use Linux, I know what terminal is and I use it, I just don't understand the full view)
Extreme? My friend, I'm afraid that yours and my definition of "extreme" differ greatly. My 9 year old son can easily walk through the grapheneOS installation steps with a fresh-from-the-factory pixel. And I'm talking about the terminal approach, not the web browser approach.
I would very very highly recommend against buying a phone with grapheneos preinstalled. Once something has been in someone else's hands, you really can't tell what has been done to it, which means that any advantage you were going for is effectively GONE.
If you're uncomfortable doing the installation yourself, then find someone who can do the job using your equipment in your presence so you can watch what they do.