I installed Version: 6.0.7.3 Build ID: 1:6.0.7-0ubuntu0.18.04.2 on a Mint 19.1 installation.
LO is the only application that cannot ‘see’ the printers is LibreOffice.
It returns: ‘No default printer found’.
The applications that do show the installed printers include:
CUPS, Abiword, Thunderbird, Firefox and Gimp
LO was installed via Synaptic.