Okay, So I have done editing using Kdenlive on Fedora. And six months ago I installed Ubuntu.
And today I tried for the first time to open one of the Kdenlive projects (which were all on a separate disk) and I got this message:
"This project type is unsupported (version 0.94) and can't be loaded.
Please consider upgrading your Kdenlive version."
Kdenlive version according to the about box: "Version 15.12.3"
What can I do short of sliding the Fedora startup disk back in?

Try with Kdenlive 15.08.0. It seems with this version they change the file format. But I can’t find the AppImage of that version.