So after spending a few hours yesterday trying to get my dock working with my MacBook Pro (15-inch, 2019) & different driver versions, I've finally been able to get the dock working thanks to a combination of a few of the support articles by DisplayLink.
I am running v.5.1.1 on the DisplayLink drivers on macOS Mojave 10.14.5.
Code:
sudo cp -r /Library/PrivilegedHelperTools/DisplayLink/DisplayLinkUserAgent.app /Applications/
To test it first, before copying to /Applications/, you can copy the app to your Desktop & run it from there. My monitors immediately displayed my desktop after starting it. After that I copied the app to /Applications/, & added it to Login Items through System Preferences > Users & Groups > Login Items, & added DisplayLinkUserAgent. Now as soon as I login after powering on, my screens show up as expected.
Wanted to post this for anyone else having the same issue.