I use this Wallpaper Engine KDE plugin.

You can download wallpapers from the Wallpaper Engine Steam workshop and load them using the plugin instead.

Are there any programs that can animate a cat to chase my mouse across the desktop? Or a guy who runs up window borders and tries to wrangle the mouse?

https://github.com/y4my4my4m/kde-shader-wallpaper only for KDE though

There's a KDE plugin for Wallpaper Engine

https://store.kde.org/p/1475528

Github: https://github.com/catsout/wallpaper-engine-kde-plugin

https://github.com/jeffshee/hidamari

mpvpaper if you use wayland compositors It doesn't work on nvidia hyprland, but nice work on intel igpu

I use mpvpaper on sway and cosmic

I'm surprised nobody has recommended Smart Video Wallpaper Reborn for KDE, but then again, it is an old thread. This is my favorite, it also allows for animated wallaper on the lockscreen.

Pretty sure I did with mplayer and/or feh but it was years ago

After seeing this thread, and the Linux wallpaper engine repo, I think I'm gonna boot into Windows and record wallpapers I like as videos, then set them as backgrounds in linux. I'm gonna be on x11 until cinnamon updates to waylan

I set mpv as the root window which worked well. I stopped using it a while back, but if you are interested, I could dig up the simple script for you (literally one or two lines iirc).

swww (wayland only)

never tried it (i don't use animated wallpapers) but it seems pretty good, not sure if it works on non-wlroots like KDE or GNOME