Linux Lite won't let me install *any* software

[Valtam]

Read this thread here, Linux Lite is not designed to work with software center - https://www.linuxliteos.com/forums/index.php?topic=508 and we recommend against it's installation. Much easier to use Menu, System, Install/Remove Software. Also make sure the user who is installing software is the one you set up when you first installed Linux Lite. If you added any additional users after an install, they will need sudo privileges to install and remove software. More info here - https://www.linuxliteos.com/manual/install.html#adduser