[Resolved]

It has come to my attention thanks to Clem at Linux Mint that there's currently a Major issue with the upgrade paths of EVERYTHING for 16.04 > 18.04, and so with this I warn everyone, DO NOT INSTALL THE MAJOR UPDATE UNTIL FURTHER NOTICE.

So, the problem here is as follows:
In 16.04, MESA got an update that makes it NEWER than the version on 18.04 (a backport), which creates MASSIVE APT Dependency Issues which, upon a person taking the upgrade path, can result in the removal of Desktop Environments, Libraries, Zenity, WebKitGTK, in other words, YOUR INSTALLATION WILL GET TRASHED IF THIS HAPPENS TO YOU.
The source comment is here: ​​https://blog.linuxmint.com/?p=3615#comment-144157
Clem has confirmed that he's in talks with the MESA team at Canonical to try and get this fixed as fast as possible, but I thought I'd also warn you people too, as his post is merely a comment on the situation and so won't get noticed fairly well.

So, what now?

It's a little too late in the day now for me to react to this situation, but tomorrow I promise that, because of the fact that the Major Update process requires an internet connection as is, I'll make use of the Major update scripts GitLab to add a blocker file which then prevents the Major Update from being commited if the file is found on the repo, and will then get the script to download it and print the message inside of it as to what's going on, for those who may be unaware.

Also, businesses, like I said, schedule it for some time LATE in the year, so that there's enough time for bugs like this to be ironed out before your computers get the brunt of this set of updates.

The Feren OS Dev