Version: 6.5.0.380, and then 6.5.0.390
I can say, my second Pro1 with original Android 9 (no root) (unlocked bootloader) has no problem to unlock Enpass with finger.
That means, the problem is between Lineage OS (similar with root or not root) (unlocked bootloader) and Enpass.
In the last days I tested a lot... sadly to confirm, it must be Lineage OS
But perhaps you have a hint or solution for it
FYI: I have so many apps (about ~10) which I unlock with my finger, only Enpass don´t want it