HMD had had an internal Android Pie beta for the Nokia 8, presumably in the process of working on a stable version for the 2017 flagship. However, this build is now out there for users to download, thanks to an XDA leaker. It can be tested via this website's forum for the phone.
https://www.notebookcheck.net/Stock-Android-Pie-beta-for-the-Nokia-8-leaked.372251.0.html