I'm running PCLinuxOS and I cannot get Kdenlive to run. I get this message

Missing app: mediainfo
optional for technical clip information
Missing MLT module: sdl or rtaudio
required for audio output
Missing MLT module: xml
required for audio/video
Missing package: Frei0r effects (frei0r-plugins)
provides many effects and transitions. Install recommended
Missing package: AVFilter
provides many effects. Install recommended
Missing MLT module: avformat (FFmpeg)
required for audio/video
Missing MLT module: qimage or pixbuf
required for images and titles
Missing MLT module: kdenlivetitle
required to create titles
Missing MLT module: glaxnimate
required to load Lottie animations

I've double checked and the packages noted are all installed.

How can this be happening on two separate systems?

The install version? (had problems then too)
If so i recommend you to use the app-image version.