I'm using Gwenview that comes with Kubuntu 19.04 and it doesn't appear to have the option to not show videos anymore. (Videos play when browsing images using the arrow keys)
This was present in the toolbar which seems to have been removed in the latest release.
Is there some other way of disabling playing videos in gwenview like a configuration file?
The option is still there and in the same place as it is in 18.04: Settings > Configure Gwenview > General.
To deal with "But there isn't a menu bar", pressing Ctrl+M will toggle the menu bar on or off in Gwenview.
Tip:
Ctrl+M does something similar in Dolphin. It toggles the menu bar and the Control icon (☰) which offers the same options but in a vertical format.
To toggle the menu's visibility in Konsole, use Ctrl+Shift+M.