The reason why GrapheneOS only supports the Pixels is that the other manufacturers are not trying to get their shit together and release a phone that is reasonably secure. It's not that GrapheneOS supports Google, it's just that the other manufacturers are worse than Google.
If a major manufacturer released a good smartphone that GrapheneOS could support, they would get new users from the set of people who want GrapheneOS. I would gladly buy a non-Pixel as long as it can run GrapheneOS.
Which means that in a way, if you buy a Pixel and install GrapheneOS, you give more credibility to GrapheneOS, making it more interesting for a different manufacturer to consider supporting them.
If a major manufacturer released a good smartphone that GrapheneOS could support, they would get new users from the set of people who want GrapheneOS. I would gladly buy a non-Pixel as long as it can run GrapheneOS.
Which means that in a way, if you buy a Pixel and install GrapheneOS, you give more credibility to GrapheneOS, making it more interesting for a different manufacturer to consider supporting them.