After going through the Wiki description of export options from the command line at Gramps 5.1 Wiki Manual - Command Line - Gramps, I understand that there is no option to run the export to SQLite from the command line since the format options (Gramps 5.1 Wiki Manual - Command Line - Gramps) do appear to have no entry for SQLite. Is this understanding correct or did I miss something?
The SQLite importer and exporter are third-party addons, so they are not included in the main documentation. There is a wiki page with a some limited details.
Update: the options appear to be correct and Gramps starts the export process, but after a short time a sequence of Python error messages pops up and the export crashes.