Update - I was able to get it working after (I believe) doing a reinstall of the kernel headers:
Code:
sudo apt install --reinstall linux-headers-$(uname -r)
I'd had issues with VirtualBox after the upgrade, and that resolved the issue with VBox. After that, I installed from the synaptic repo (did not use the standalone). I STILL got an error about evdi, but my monitors started working, so I'm good.