GrapheneOS is designed for everyone, including average users. It does not require a high threat model, and the features it provides are not only useful to people with high threat models.

Contrary to popular belief, exploitation of vulnerable devices is a lot more common, and a lot easier than people pretend it is. You dont need to be targeted either, mass exploitation can, has, and will occur.

LineageOS does not have privacy, security, or usability comparable to GrapheneOS. LineageOS is missing many important features and falls behind android updates. GrapheneOS will be the far better choice in all 3 of these categories.

The features GrapheneOS provides, such as the network permission, cannot be replicated with a firewall app. The network permission properly covers all forms of network access for an app, where firewall apps do not have the ability to prevent all network communication. They are leaky.

The AGNSS servers and proxies are very, very tiny aspects of what GrapheneOS provides. You would be losing out on many more high impact privacy, security, and usability features.

Root access and an unlocked bootloader are insecure, even for low threat models. These devices are vulnerable and should not be used for any sensitive data.

LineageOS is not the better choice for any privacy, security, or usability usecases relative to GrapheneOS.