HMD CPO Juho has just announced Android Q developer program for Nokia 8.1. The first preview build that Nokia 8.1 will get is in fact Android Q Beta 3.
— Quho Sarvikas (@sarvikas) May 7, 2019
So, you can just click on the link provided below and enroll to the developer program for getting the Android Q developer preview. Just keep in mind it can be a bit rough ride. Currently, the preview build needs to be flashed manually and OTA update is not available.
There is no option of rolling back to Pie even if you want to as clearly mentioned on the preview page.
For the time being, the developer preview build can only be flashed to the device by sideloading (manual flashing). There are certain steps in the “Manually install the developer preview” section that must be completed before attempting to flash a device.
Failure to correctly flash your device may render it completely unusable, making it impossible to reset it to its original state.
We are currently unable to support rollback to Android 9 Pie. We hope to have manual rollback support available by 16 May 2019. The website will be updated as soon as manual rollback is available.
If you have any doubts about sideloading, or rollback to Android 9 Pie, we recommend waiting for full over-the-air (OTA) upgrade and rollback support.
Also, not all Nokia 8.1 variants are eligible to get the preview and HMD has asked users to check the build number before going ahead with installation.
Please note, the program currently only supports models TA-1119, TA-1121 and TA-1128 (go to Settings > System > About Phone > Model & hardware) and associated 00WW images (scroll further to Build number) – if you see reference to “00WW”, then you’re good to go. If it references to “00CN”, then please do not take these builds.