Bump.
Well, according to this XDA post, you have to use this open tool to unlock bootloader 1st:
According to this XDA 3ad the device is treble-enabled, so you can try \e\ GSI builds:
https://forum.xda-developers.com/t/megathread-project-treble-megathread.3778767/
Then you can also try to (unofficially) build yourself:
Hope that helps/inspires !