(I cannot test with Lnux.)
(Not quite for sure: ) There should still be an option to the wanted effect during installation / change installation.
(For sure concerning LibO5.3.x.y on Win:) The option you are looking for is still present under >'Tools'>'Options'>'LibreOffice'>'Memory'
(Not much use with this option imo.)
In addition: To place a link to call the software into the systray is a different thing. I always do this but never activate the quickstart option ‘Load LibreOffice during system start-up’.
(Editing with respect to the comments below:)
ToolsOptionsLibreOfficeMemory.png
In rare cases a corrupted user profile may spoil a menu or a dialog.
(There is a variant of the ‘Memory’ settings dialog not containing the quickstarter option. It is used for PortableApps versions where the option is not appropriate. I do not know in what way the choice is managed.)