It does work now, last appimage from 09/17/2020:
https://www.onlyoffice.com/en/download-desktop.aspx
My launcher .desktop for menu & to pin it on the taskbar if needed
Modify paths to appimage & icon, save it in .local/share/applications/ as Only Office Desktop Editors.desktop
[Desktop Entry]
Version=1.0
Terminal=false
NoDisplay=false
Icon=YOUR PATH TO ICON /asc-de-128.png
Type=Application
Categories=Office;
Exec=YOUR PATH TO APPIMAGE /DesktopEditors-x86_64.AppImage
MimeType=application
Name=Only Office Desktop Editors
GenericName=Office
Comment=Secure office and productivity apps