Currently, The kdiff3 website (https://apps.kde.org/kdiff3/) only lists flathub and appstream buttons and a link to the binary-factory jenkins https://binary-factory.kde.org/ where I then have to filter myself to find some nightly build for kdiff3. There are, however, well-working release builds for kdiff3 here: https://download.kde.org/stable/kdiff3/?C=M;O=D I would like to suggest replacing the binary-factory link with the download.kde.org link, because that actually lists releases.
(that latter link is only found in the gitlab README.md)