How "hardened" is it? Can you completely control network traffic and permission access of every installed app?
For example, if you wanted to spoof the android_id (something you usually can't do with regular permissions) to some app, could you do that?
Also, is app storage isolated? This is a new feature in Android 10 but a pretty easy way to allow for cross-application tracking/fingerprinting in earlier Android versions.
I currently run Lineage with microG but I still had to get root access to effectively counter those things.
No need to "harden" it after you install because things are locked down by default.
I've been using it for the last six months and I think it's fantastic.