They really don't. It's just that development of custom roms like GrapheneOS are centered around Pixels. Plenty of other devices have unlockable bootloaders. The custom rom scene though is so small that concentrating on a couple devices is the only way to keep development moving forward though. Same reason why Asahi Linux is the only option on Apple Silicon Macs.

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wkat4242 4 days ago | parent | next [-]

Many have unlockable bootloaders (though the number is rapidly declining with Samsung closing up). But not many have relockable bootloaders. This is one of the things that grapheneos have set as a minimum standard, hence the reliance on pixels. There's a few other specific things that the titan chip provides which they rely on but the relocking is the main thing.

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ycombinatrix 4 days ago | parent [-]

To be more specific - relockable with a custom AVB key. I think most devices can relock with the default Google AVB key.

	▲	wkat4242 4 days ago \| parent [-]
		Well they can but not with custom firmware installed. As grapheneos is custom firmware, the google key makes no sense in this context.

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subscribed 4 days ago | parent | prev [-]

"unlockable bootloader" is the requirement to flash anyone alternative on the phone, yes, but the GrapheneOS you mentioned will support _any_ device that is "flashable" and secure enough: https://grapheneos.org/faq#future-devices

Currently it's only Pixels from 8 up.

Other alternative firmware projects don't seem to be too concerned about security (eg they don't support relocking bootloader, don't support secure boot, don't release patches for months), so they're not really in the same ballpark ALTHOUGH I agree that they still might be better option than stock OS on the device abandoned by the vendor.