UBports doesn’t uses Android Linux Kernel for Librem 5, Pinephone, Raspberry Pi.
The issue is detailed in this new blogpost from UBports foundation : https://ubports.com/fr_FR/blog/notre-blog-1/post/october-2019-status-of-ubuntu-touch-on-librem-5-smartphone-250
And, remember https://puri.sm/posts/ubports-ubuntu-touch-on-librem5-collaboration/ .
At this time of april 2018, it was very far from what we read now: you will get devices to contribute Ubuntu Touch after every one !