I got Havoc ROM GSI working flawless on my old pixel 2!
Were you able to install the Pixel 3 apk on your Pixel 2 while running Havoc OS? I followed your tutorial for the Havoc installation, and it works great, but the Pixel 3 app crashes every time I open it. I tried the app with night sight, and the older version of the app, but no luck.
Sorry… I meant the Pixel 3 CAMERA app!