@Zach Patch 

I think Dell tech rep have limited actions as far as windows update troubleshooting.

If they did this ,they would spend all day trying to find solutions with so many win updates.

A few suggestions if you can login:

1. Uninstall KB4586876  ( all settings/update & security/view update history/ uninstall) and reboot, if that solves the problem
2. Make sure you have the latest video driver
3. Download the KB4586876 from the window catalog and re- install locally, sometimes the win update one does not work correctly  https://www.catalog.update.microsoft.com/Search.aspx?q=4586876
4. you can also check your window installation  with the win 10  sfc and dism utilities

        if you don’t know how to use these, download the tweaker utility ( I use this very often)

         https://www.thewindowsclub.com/ultimate-windows-tweaker-4-windows-10

         bottom right options. That will check your win 10 installation and make corrections if some are needed.

Beside these there is the window startup repair.

        .

It was just rolled out yesterday: https://support.microsoft.com/en-us/help/4586876/kb4586876-cumulative-update-for-net-framework

I'm not seeing a clear connection between a net framework update and the SLI GPU issue.  It might be coincidental since you had to restart the computer.  Were there any other changes, software, anything different or updates that you added since you last restarted?  Have you tried checking event viewer, and running the f12 epsa diagnostics?  

Of course you can try rolling it back or uninstalling the update like noted.