When starting a LibreOffice component, e.g. lowriter or localc, it may complain with the above warning about not being able to start javaldx.
In my case indeed some LibreOffice packages were not installed by default. To fix the problem run
sudo apt install libreoffice-java-common
This in turn will also install a few additional packges:
The following NEW packages will be installed
liblibreoffice-java libreoffice-java-common libunoloader-java ure-java