Comment 10 for bug 1854183

This command also works as a work around
sed -i 's/.*SpreadsheetDocument.*ooSetupFactoryWindowAttributes" oor:op="fuse"><value>/&57,38,1805,980;1;0,0,0,0;<\/value><\/prop><\/item>/g' ~/.config/libreoffice/4/user/registrymodifications.xcu

Replacing the "57,38,1805,980;1;0,0,0,0;" with whatever are good values for your display size as taken from "~/.config/libreoffice/4/user/registrymodifications.xcu" when LibreOffice opens OK.