Although it beta tested Android 8.0 Oreo for its first smartphone last year, ultimately Essential decided against releasing that version of the OS to every single customer (not that there are very many of those, but still). The company said 8.0 wasn't stable so it would directly send out the 8.1 variant of Oreo to non-beta testers.
That day has finally come. Essential has officially announced that the rollout of Android 8.1 Oreo for its Phone is underway. You can apparently already check for the update in Settings and it should show up. If it doesn't, don't fret - the release may be one of those staged affairs which only go out to a subset of devices first.
Anyway, we assume it will make its way to every single Essential Phone out there in a few days. And hopefully this version will prove to be stable, as its beta test started around one month ago.