Just joined the forum, and I'm new to Kdenlive as well.
I plan on using Kdenlive for my home and motorcycling videos.

First, my hardware:
I have a Lenova Think Station P300, 3.5 gig processor and 32 gigs of ram,
with a brand new GeForce GT 710 video card.
running Linux Mint 19.1

I loaded the latest version of Kdenlive from the Appimage, and it seemed to install ok.
But when I dropped a clip onto the Project Bin, and then attempted to watch it
in the clip monitor, the video flashed on and off, and jerked all through the clip.
If I added the clip to the time line and then tried to watch it in the project monitor
I got the same results, flashing jerky video.
Any ideas why?

(I have since switched to 17.12.3 from the Mint repository but I'd like to
use the newest version if possible)
Thanks in advance guys.
George

GPU is not supported from Kdenlive so far. You say under Kdenlive 17.12 it runs OK/smooth but not under 18.04 and later. Correct?
Make this test with the AppImage only.

I never tried 18.04.
I only tried 19.08.0a and that was the version that gave me trouble.
But yes, under 17.12.3 it runs smoothly.

P.S. I don't know what you mean by GPU.
Please explain?
And thanks for responding to my question, Merlimau!

George