Maybe this helps:

Go for VA administration (port 9443), Configuration, License: there is the requested information. Maybe there are other spots too.

If you are running 24.3, then you are beyond the Filr 5 version.  You can also log into the 9443 interface on each of the appliances and in the upper right corner you will see the version.

From one of my Filr nodes:

Aloha, Bobert
That's the version of Filr itself.
This concerns the version of the underlying appliances.

Correct.  In order to get to 24.3, you would have had to go to version 5 or would have had to start at version 5.  

Correct.  In order to get to 24.3, you would have had to go to version 5 or would have had to start at version 5.  

Aloha, Bobert
My apologies, you are correct.

The problem is in a lack of documentation updates.

If you look at the documentation for Filr 23.2 through 24.4, the sections on upgrading are all titled "Section 10.0, Upgrading from Filr 4.3.1.2 to Filr 5.0".
The first statement in those sections is "Review the following sections before you upgrade your Filr 4.3.1.2 setup to Filr 5.0".
Likewise the "Support Matrix comment is:
"You must update to the latest 4.3.x patch version before upgrading to 5.0."

This was a brand new installation so these appliances started out at 24.3.

When I saw the statement in the 24.4 documentation to "Ensure that the version of the Filr appliance is 5.0 or later.", I made the assumption that they were referring to the underlying SUSE appliance, when all they were saying that you can't upgrade from Filr 4.3 or earlier to 24.4.
You have to be at Filr 4.3.x or later.

Instead of simply copying-and-pasting that section from one set of documents to the next, there should be changes that refer to the specific Filr version in question.
Section 10 should be titled "Upgrading to Filr <whatever version>"
Then follow that with:
"Review the following sections before you upgrade your Filr setup to Filr <whatever version>."

Then change section 10.1 to
"You must update to the latest 4.3.x patch version before upgrading to Filr <whatever version>."