Make sure of the consistency of your system, that your packages and files are as up to date as possible, and then that your installation is freshly from a repository.
You can accomplish all this by simply updating your system, the simplest and most certain is by using zypper
Of course, that assumes that you are installing from your openSUSE repositories and not from somewhere else.
If necessary,this is the software search for your app
erlangen:~ # zypper in youtube-dl-gui
Loading repository data...
Reading installed packages...
Resolving package dependencies...
Problem: nothing provides python-wxWidgets-3_0 needed by youtube-dl-gui-0.4-1.8.noarch
Solution 1: do not install youtube-dl-gui-0.4-1.8.noarch
Solution 2: break youtube-dl-gui-0.4-1.8.noarch by ignoring some of its dependencies
Choose from above solutions by number or cancel [1/2/c/d/?] (c):
This is solid evidence for a problem with the package. You may search for alternatives:
erlangen:~ # flatpak search youtube
Name Description Application ID Version Branch Remotes
Shotwell Popular photo manager org.gnome.Shotwell 0.30.10 stable flathub
FreeTube An Open Source YouTube app for privacy io.freetubeapp.FreeTube 0.7.2 Beta stable flathub
Gydl Download content from sites like YouTube com.github.JannikHv.Gydl 0.1.1 stable flathub
Video Downloader Download videos from websites like YouTube and many others com.github.unrud.VideoDownloader 0.2.9 stable flathub
MoonPlayer Video player for playing and downloading online videos from YouTube, Youku etc. com.github.coslyk.MoonPlayer 3.1 stable flathub
OpenShot Video Editor An easy to use, quick to learn, and surprisingly powerful video editor org.openshot.OpenShot 2.5.1 stable flathub
Notes-Up Your New Notebook com.github.philip_scott.notes-up 2.0.2 stable flathub
Forklift Video and audio download application com.github.Johnn3y.Forklift 1.0.0 stable flathub