Unable to update graphics driver on Ubuntu 18.04 - broken dependencies


I am attempting to update my graphics card (NVIDIA GEForce GTX 950m) on a fresh install of Ubuntu 18.04 by using the following install guide: Installation Guide Linux :: CUDA Toolkit Documentation

However, I am recieving the following error:

ubuntu@ubuntu:~$ sudo apt-get install linux-headers-$(uname -r)
Reading package lists... Done
Building dependency tree       
Reading state information... Done
linux-headers-5.4.0-81-generic is already the newest version (5.4.0-81.91~18.04.1).
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies:
 cuda-drivers-465 : Depends: nvidia-465 (>= 465.19.01) but it is not going to be installed
 nvidia-465-dev : Depends: nvidia-465 (>= 465.19.01) but it is not going to be installed
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).

I have tried “apt --fix-broken install”, but I get the following error (eventually):

Unpacking nvidia-465 (465.19.01-0ubuntu1) ...
dpkg: error processing archive /var/cache/apt/archives/nvidia-465_465.19.01-0ubuntu1_amd64.deb (--unpack):
 trying to overwrite '/usr/lib/x86_64-linux-gnu/libGLX_indirect.so.0', which is also in package libglx-mesa0:amd64 20.0.8-0ubuntu1~18.04.1
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)

Not sure what these errors mean or what dependencies are broken. Also, I have tried other solutions from the internet, but these have not helped. Is there a way to purge my install and start from scratch?

Any help would be greatly appreciated. Thank you!