[NancyV]

thanks for your post steelvoltage, it gave me some progress towards a solution

Originally Posted by steelvoltage

I was able to fix the issue this morning.

Steps that I took:

Uninstalled the displaylink driver.
Shutdown my mac and entered recovery mode.
Opened up the terminal and ran:

kextcache -i /Volumes/Local

Note: Local is the name of my disk. Yours may vary.
The command returned a string/id/guid (not sure what it entails), but there was no error message.

reboot

After it booted back up, I opened up terminal again.

kextcache | grep DisplayLink

The grep returned nothing, which now I knew the driver was gone completely. Grep is a regular expression search, meaning it returning nothing is what we want here as we cleared the cache.

I installed the beta driver and it rebooted.

Afterward, success!

this solution got output to my 2 DisplayLink driven external monitors, but required some extra work in the system preferences.
reboot broke it all again

Steps:
1. uninstalled DisplayLink driver
2. rebooted and checked the kextcache to verify it was cleared and verified DisplayLink software no longer installed
3. reinstalled DisplayLink driver v5.2(15)
4. rebooted

Results: 2 external DisplayLink monitors are recognized by the OS (cursor displays on each) but only shows black screen. app windows moved to the monitors do not display, nor does the desktop background image

5. Opened System/Preferences/Displays
Selected: Arrangement Mirror Displays
all external monitors display everything perfectly
deselecting 'mirror...' and the DL monitors go back to black, but clicking on each monitor in the arrangement display shows the thin red line indicating another monitor adjacent to the main display
Selected each of the external monitors in turn and selected "Optimize for display"
Unselected 'Mirror Displays" and all are working as expected

6. Rebooting computer - external DisplayLink monitors return to black w/ cursor state.

any other thoughts or suggestions welcome ... I'll try anything at this point. this is my work computer.

Thanks, All!