From what I have found, the start of the upgrade path should be:
FA 2.3.19 -> FA 2.3.26 (old server)
FA 2.3.26 -> 2.4.1 (old server, includes database conversions)
But what then?

I assume at some point FA 2.4.X does not run on PHP 5.4 anymore and the next version 2.4.Y does not run on PHP 8.4 yet. I have not been able to find the PHP requirements for each FA version.

I think I need to find 2 versions of FA which
- use the same database format
- the older version runs on PHP 5.4
- the newer version runs on PHP 8.4
So I would export the database on the older version, followed by an import on the newer version.

Does that even exist? Or is there a better way?