Nextcloud Update to 21.0.3 - failed

I don't know about you but Nextcloud is one of those self-hosted apps that when it's working, works really well. But updates under Nextcloud for me personally always provide a level of anxiousness.
As a result of this elevated heart rate during this update process, I have always created quite an in-depth backup plan in case I needed to roll back.
Today I have a two-hop update, starting initially on v20.0.11. Going to v21.0.1 then finishing on v21.0.3 which as of today is the latest stable release.
Everything went according to plan through the first two updates, however, when I finished v21.0.3 this is where I ran into a couple of problems.

So as the message suggests, try running the OCC command and see if you can resolve it.

Well, nope that was a fail. APCu is not available??
Checking out a couple of forums I didn't really see what I was looking for exactly but I knew I was close.

Looking at these it wasn't really clear exactly what was going wrong.
Finally, I came across this post;
A quarter of the way down, I came across the following post and noted that someone actually installed these missing modules to see if it would work.

I gave it a shot as well to see if it would have any impact on me.

Try again running the OCC command.

Wait what! Same error message, but now I am missing Redis? Okay lets try it again.

Let's try the OCC command again..

Yes its working!!

The message is gone. Now to get these next errors sorted.
So long story short, I was missing the APCU and Redis module for some reason. Not sure why or how but that was what was needed to fix the error I was seeing.