Nextcloud not web accessible after upgrading from Ubuntu 16.04 LTS to 18.04 LTS

Nextcloud version: 15.14
Operating system and version: Ubuntu 18.04 LTS
Apache or nginx version: 2.4.29
PHP version: 7.2.24

The issue you are facing:
I had a working instance of Nextcloud 15.14 on Ubuntu 16.04 LTS. Obviously, 16.04 is very old now. I was doing some other maintenance on my host server so decided to do maintenance on my nextcloud VM as well. Everything worked fine in the ubuntu upgrade process and the VM is now happily on 18.04 LTS, however Nextcloud just gives a 500 error when viewed in IE, and on firefox it just shows a blank white screen.

I’m familiar with using linux servers, but it’s been a long time since this has been my normal job, so troubleshooting this is a bit out of my wheelhouse. Does anyone here have advice on how to resolve this problem?

Well of course right after I give up and make a post I finally find the solution. For anyone else running into this, this thread resolved my problem - Upgrade question Ubuntu 16.04 to 18.04 server upgrade