Enable GPU (hardware acceleration) on ubuntu for pi 4:
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You will need to have the drivers installed as well as pi config file have the gpu reconised.
It does not matter what order as long both are complete.


You need all of these drivers to enable gpu support with a Desktop Enviroment:
sudo apt-get install libgles2-mesa libgles2-mesa-dev xorg-dev

If you just want base GPU access for cli use, you just need this:
sudo apt-get install libgles2-mesa

For the hardware, 
In the /boot/firmware/config.txt file add these lines:

dtoverlay=vc4-fkms-v3d
max_framebuffers=2
gpu_mem=256

This should enable hardware acceleration.

Note about GPU memory, unlike x86, ARM does not need much GPU memory and it could actually be harmful to have a lot. It is best around 256-512mb for systems with 1GB ram or more.

To test if GPU is enabled/active, input the commands of:
cat /proc/device-tree/soc/firmwarekms@7e600000/status
and
cat /proc/device-tree/v3dbus/v3d@7ec04000/status
If they return 'okey' then the GPU is sucessfully installed and active
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Sources: https://www.dedoimedo.com/computers/rpi4-ubuntu-mate-hw-video-acceleration.html
https://www.raspberrypi.org/documentation/configuration/config-txt/memory.md
Date Got: January 15th, 2021