Sony is pretty good about letting the open-source community have a field day with its devices thanks to the company's Open Devices Program. Two new phones just got added: Xperia XA2 and Xperia XA2 Ultra. That means that they are open to flashing custom versions of Oreo.
As an added bonus, Sony also provides a guide to help you build from AOSP. The company is careful to point out that all of this is meant for developers, since the early stage nature of it can lead to some instability. Those of you who are interested in contributing can hop over to Sony's GitHub project pages to take part in the community.
All in all, I think this is a great thing and I wish more OEMs did this. Good job, Sony. Keep it up.