Lineage OS

Depends on your use case. If you're the type of person that uses their phone beyond the 2-3 Android version update cycle ("life of the phone"), LOS allows you to enjoy newer versions of Android rather than being stuck, potentially, several versions behind. I used a Galaxy S5 for far longer than I'd like to admit. 😅

Yes, but not entirely.

You still have an OS with less tracking built in, and you have more control over apps & permissions (like being able to entirely block data usage for certain apps at the system level).

Yes, it's still easier for Google to invade your privacy with GApps, but let's be frank, the amount of info they can gather through Android Auto even 1 wasn't linked to other system apps is pretty staggering. They know where you are & where you're going at any given moment. They have access to your notifications, including messages, what music or podcasts you're listening to, etc...

There's just unfortunately no comparable alternative, aside from just mounting your phone on the dash with a phone app

Depends on what you think the point of LOS is.

At its core it is pretty much the same as the custom android versions of the phone manufacturer OS' but allows you to not get GApps if you don't want them