I have a perfectly good phone whose bootloader can be unlocked and I can install LineageOS or other AOSP installations there but all I'm aware of and I've researched come short on the sandboxing and permissions. I'd be willing to use GrapheneOS without support for specific security hardware (if only they supported that configuration) just for the features mentioned but Pixel phones are just too expensive. I've always been more than happy with a decent low-tier phone and I don't see a technical reason to change that. Nothing wrong with my phone.
But the whole idea of GrapheneOS is the reason why it (currently) only runs on Pixels. On other phones you can run anything based on LineageOS...
I don't want GrapheneOS to compromise on that: if I didn't care about it, I would use any other alternative. To me it's a bit like saying "I would be using Linux if it was a lot more like Windows" (that's something I often understand when Windows users explain what it would take for them to use Linux). But I, as a Linux user, really don't want Linux to look a lot more like Windows.
There's first-world, upper-middle-class affordable (~$500) and then there's global affordable (<$250).
Currently I can get brand new Pixel 8a on ebay for £250 or similar, and refurbs from "flawless" to mint" conditions for half of it.
Still good enough.
Doesn't help with the current situation though but I hope the partnering between Motorola and GrapheneOS is still up and going in a few years when I'll next have to replace my phone.
That said, I think the marketing of GrapheneOS could be better. Every introduction of GrapheneOS I've seen paints the image of Graphene being "Absolute security, no compromises", whereas in reality GrapheneOS is the most "Things need to work, no compromises. Then make the rest as safe as possible" custom ROM that I've used thus far (in particular regarding them allowing you to install Google Play, rather than using MicroG).