If I double-click on a .docx file in KDE Dolphin, such that it opens with LibreOffice (which is installed as flatpak), I get an error that the file is not found on disk. Turns out it's because the filename contained a special character ("ä").
I don't even know where to file a bug about this? Candidates are Dolphin, flatpak, LO flatpak manifest, LO itself?