Comment by saidinesh5

A few years ago, Lineage was just a customizable tinkerer friendly AOSP. It served as a base for a lot more Android distros. It was just a smoother Android variant with features like double tap on the notification bar to sleep, better integrated root support, more built in theming options.

Graphene OS was only available for a few Pixel Devices whose source was fully available and mainly focused on security features like improved permissions and more anti tracking features.

To give an example, a company I worked for shipped it's phones with a Lineage OS base with a few patches from Graphene OS to replace default ntp and connectivity check servers.