I have used the Windows version of OnlyOffice and attempted to install on Linux via Flatpac and there seems to be an issue where the interface seems to be very basic and primitive. Using the latest version on Flatpak and checked with Fedora KDE and Kubuntu KDE with the same results. Even worked with Claude AI and it determine that..
Found it — this is a known interaction: libreoffice-kf6 (which got installed as a dependency) makes LibreOffice inherit KDE’s actual color scheme for its widget chrome, regardless of what you pick in that “Themes” dropdown — the dropdown mostly governs icons/background, not the toolbar frame itself. Since your KDE global theme is dark, that’s what wins.
There’s a way to decouple it — force LibreOffice to use its own built-in rendering instead of matching KDE:”
i opted not to do this and was wondering if there is a fix.