I absolutely can recommend LineageOS (used to be CyanogenMod). I installed it for the first time about a week ago on my phone, and I couldn't be happier.

Rooting it is straightforward, and the first thing I did was to install a firewall, and AdAway (so I get system wide ad-blocking and tracker-blocking). It's an incredible feeling that for the first time in forever I'm more in charge of what my phone does.

The only caveat is that the support from LineageOS for less popular phones isn't great (unless you get lucky!) but if it does work on your phone, absolutely go for it.

Also, assuming your device has a good maintainer or maintainers, security patches arrive in days rather than the months-if-ever it can take manufacturers to release updated images and then carriers to roll them out.

Lineage and Copperhead are still AOSP, warts and all, under the covers.

An interesting ticket [1] is to try and boot devices using an upstream kernel. This would enhance the utility of older devices, given the community fork of Ubuntu [2] is abandoning devices stuck on a Jelly Bean kernel (v3.4) without serious back-porting.

[1]https://github.com/postmarketOS/pmbootstrap/issues/12 [2]https://ubports.com/blog/ubports-blog-1/post/ubports-communi...