I installed LineageOS 16 on my Nexus 6p to have better privacy. It's an Android Custom ROM that you can use without a Google account and Google apps. So no tracking or selling of user data. I love that.
The drawback is that if you don't use a Google account, you can't have the Google Play Store. So you have to use alternative app stores, like Fdroid. Fdroid is great because it only has open source software. That is perfect for my privacy project. Of course you can also sideload APK files to install apps if you want. I did that with the NordVPN app and Firefox.
It was a bit of a hassle to install LineageOS. You have to fiddle with trying to unlock the boot loader on your phone. You don't have to root though, but I did that too with Magisk root. Because then I can do even more with LineageOS and apps.
So al in all, it was a fun project to "hack" my Nexus 6P.