In what is probably the best customer support experience I've had in my life, I reached out to DisplayLink about the potential conflict and received a follow up response no more than 5 minutes later. Here's the scoop:
- DisplayLink has recently been made aware of the issue and is currently testing a new release that includes a fix for it.
- 11/24 update: per my support contact at DisplayLink, pending no issues are found with the current build the ETA for the updated driver is mid-December.
- There is a better workaround for this issue than the one previously recommended of disabling Protected View:
- Open an Office application (I used Word) and go Options > Advanced and check the
"Disable hardware graphics acceleration" box and click OK.

I am happy to report that this resolved my issue and I am now able to preview attachments within Outlook with Protected View still enabled. I didn't even have to reboot for the change to take effect.
Big tip of the hat to DisplayLink for their stellar customer service and follow up on this. Hope this information can be of help to others dealing with this issue.
Thank you! Thank you! Thank you!!!! I have been trying to figure this out for quite a while. I would have never guess that a DisplayLink device would be causing this issue! You are my Super Star!