Linux OS on Gen 1 Pixel tinkering

I have an donated Gen 1 Pixel phone so that I can experiment trying a new OS on it. I use linux mint on my laptop but still consider myself a beginner. The goal is to eventually do this to my main phone (A galaxy S8) but I wanted to get a feel for how to do it. I'm stuck on the OS, I only use the phone as a clock, texting, and occasionally a call. Internet isn't a huge deal but it'd be nice in a pinch. I'm looking for an OS that's easy to use, privacy & security. Any recommends/guides?