But I like my Moto G which has an SD slot, 3.5mm audio jack, more battery life, stylus, and easier to replace battery than a Pixel. So I'd rather not downgrade my phone just to run Graphene. Why would I want a TPM chip anyway? Those are mainly intended to enforce DRM. I can believe no backdoors in the OS, but no vulnerabilities in the hardware? That's a stretch, think of the Intel management platform and everything else (https://tpm.fail/). If the hardware was really that secure, the govt would block its manufacture. There would also be no market in HSMs. I can believe in TPM slowing attackers down but that's about it.
Anyway I distrust my phone enough to not have anything super sensitive on it. I don't think a TPM chip would change that. So I'm still skeptical.
Do Graphene users really bother to enter a 128 bit decryption key to unlock their phone? How do they do it? I've thought of a few ways but am unfamiliar with anyone using them.