(#5azncma) @firstname.lastname@example.org Depending on what your phone actually is, you can likely just whack LineageOS on it and get more or less the latest Android on it. Device list here. If it already has Oreo on it I assume it’s not more than 4 or 5 years old so it will depend on your phone’s bootloader I guess.
I put LineageOS on one of my old Samsung Galaxy S5s (from 2014!) recently, now it rocks the latest Android 😎