It is not exporting a file to the "md" format. When using this option, the file becomes empty.
Either check back in February 2026 or try an unstable build. https://dev-builds.libreoffice.org/daily/master/current.html https://wiki.documentfoundation.org/Installing_in_parallel/Linux#Automated_installation *** This bug has been marked as a duplicate of bug 160734 ***