Ok, apparently after looking for some specs on the ethernet controller, some questions about similar motherboards on hardware forums and then some questions on the Ubuntu forums, I could narrow down the issue to the "forcedeth" driver, attributed to the nVidia nForce part of my motherboard (I assume it is some sort of I/O controller, as it also controls onboard audio, hard drives and whatnot). [EDIT: This seems to be a problem on most, if not all, ASRock motherboards running AM3+ CPUs, so if thats your case, the following solution might work out for you.]
Here is the solution that worked for me:
Booting into Recovery mode through GRUB.
Then on the recovery options, I had to select GRUB to change my system from "read-only" to "read-write".
Then I went on ROOT and did the following commands:
# rmmod forcedeth
# modprobe forcedeth msi=0 msix=0
And Ethernet is now working.
But, that only worked until I rebooted, so after a couple of hours looking into articles on my phone, I reached the following solution to make it so ethernet is working every time (also, I was having issues shutting down/restarting, those were fixed too).
Insert the following on terminal:
echo "options forcedeth msi=0 msix=0" | sudo tee /etc/modprobe.d/forcedeth_options.conf
Insert your password, and then
sudo update-initramfs -u
And bam, it is working.