For many years, I had an installation of KnowledgeTree for our small charity “Nazareth Kinderheim Kenia e.V.”.
Unfortunately, it has not been maintained anymore for many years, and the replacement of PHP5 with PHP7 forced me to do something.
I finally settled for SeedDMS as a replacement, and I really like it!
See instructions how to install SeedDMS in a shared hosting environment, at Hostsharing: https://wiki.hostsharing.net/index.php?title=SeedDMS_installieren (in German).
To export the files from KnowledgeTree, I made the decision, that I would ignore deleted files, and would not need the history of files, so only the latest version of each file. That made the migration much easier.
I found a Python script by Ben E. C. Boyter at https://boyter.org/2015/09/exporting-documents-knowledgetree-3-7-0-2/ which was a good start. I found only two issues with it: it would restore even deleted or archived files, and it would restore a random version of a file, not the latest version. So I fixed the Python script, and you can see it here as a gist: https://gist.github.com/tpokorra/71526bc60ced2649dba2c528d5cd2259
There is an import function in SeedDMS, where you can import from a directory on the server, which minimizes the used bandwidth. Alternatively, you can use WebDAV to import a lot of files at the same time.