[edit: this was meant to be a reply to another post, which I can’t find anymore now, not sure what happened. still learning my way around Lemmy / Jerboa…]

GrapheneOS is designed to preserve the security model Android was built around, which also means you do not get root access (but neither does Google as it’s completely independent). This is the reason it can only be installed on Pixel phones, as they’re the only ones that allow you to re-seal the boot loader after installation, preserving the security chain. I’ve been using it for years now to great satisfaction: it feels very solid and secure, yet is surprisingly functional (all apps I need work fine, including tricky ones like banking with NFC payments).

LineageOS allows you to root it, which is great for poking around, but it also implies breaking a lot of Android’s security guarantees.

If you value security and privacy above all, get a Pixel and install GrapheneOS. If you want to mess around freely even if it means being slightly less secure, go for LineageOS.