Problems with Nvidia drivers on Ubuntu 18.04 Mobile Precision 7530

I have a Mobile Precision 7530 laptop with an i7-8750H and Nvidia Quadro P2000 GPU. The operating system is Ubuntu 18.04 (came installed by Dell). I'm running into issues installing the Nvidia drivers on this computer. After installing with 

sudo apt-get install nvidia-driver-440

the laptop, on boot-up, just shows the message "Started bpfilter" and hangs. I can still access the command line with ctrl-alt-f1. If I uninstall the drivers with

sudo apt-get remove --purge nvidia-*

the computer is able to boot up normally. I used nvidia-driver-440 because this was recommended by "ubuntu-drivers devices" but I've also tried 390 and other versions and gotten the same issue.

I'm also unable to use an external monitor with this laptop, which I believe is a related issue. Without the Nvidia driver installed, if I plug in an external monitor through HDMI, it is not recognized. If I then go to system settings, the desktop goes black and gives me the same "Started bpfilter" message. If I then unplug the monitor, I get kicked out to the Ubuntu log-in screen.

I have tried the following without success:

• Tried modifying /lib/modprobe.d/nvidia-kms.conf as described in this post. Did not seem to have any effect.
• Tried the fixes described here.
• Installed driver using the .run file from https://www.nvidia.com/Download/index.aspx. Gave the same "Started bpfilter" hang.
• Tried lightdm, gdm3, and slim display managers. Lightdm gives me the same result. slim gives a black screen on boot-up (no "Started bpfilter" message). With gdm3 activated, (and with the "WaylandEnable=false" line in /etc/gdm3/custom.conf commented out), I am able to get to the log-in screen with the Nvidia driver installed. However, I cannot log in - after entering my password I get sent back to the log-in screen.

Really appreciate any help or advice with this. Thank you!