That enabled me to open/save files on an external network hard drive, using the system file manager. 5.2.0.4 has a new system: although I can open files I cannot modify them (permissions will not be an issue) or save new files except to my local drive.
In case anyone else has the same problem, I have found that the answer is to install libreoffice-gnome on top of the upgrade, at least for Ubuntu/Mint distributions. That has brought everything back for me and all is well again.