Nokia 7 plus users who upgraded to Android P beta (DP1) can now download and install the DP2. Nokia Mobile has also uploaded the new Oreo downgrade package for those who do not like the preview and want to revert back. The new Developer Preview 2 for Nokia 7 plus is versioned 3.08B.
You currently need to download the upgrade package manually and flash it via ADB. The website does mention that the support for OTA delivery is close. So, you might wanna wait some more time to get a much easier upgrade and downgrade without needing a PC.
The Developer preview program is open to all users of Nokia 7 plus. But it is recommended that only developers & experienced users take up the beta update. These early builds may still have missing features, bugs and vulnerabilities.
If you are interested in installing the DP2, then you can do so from the Nokia website.