To solve problems with LO I inadvertently installed several versions, including .deb file, flatpack, and Software Manager. What a mess!
I have tried uninstalling using Software Manager and the purge command, but LO is still there. I think it is the Flatpack version.
How do I remove all traces of LibreOffice?
flatpak uninstall org.libreoffice.LibreOffice
and then remove the user profile, see LibreOffice user profile - The Document Foundation Wiki.
Thanks erAck.
There were still problems so I gave up and reinstalled Linux Mint!