PSA for Linux video editors: Use the AppImage for #kdenlive not the PPA.
I had this awesome editing experience yesterday with the latest kdenlive and was delighted with my results.
Then I rendered and half the video turned out just black with audio. I did some troubleshooting, then 90% off the video came out black. Couldn't fix it. Went to bed disappointed.
Woke up, thought to try the AppImage, rendered out first time.