To open a LUKS container file in Thunar file manager in Linux, right click on the container file and select the option Open with Disk Image Mounter. This way, the LUKS container will appear as Device in thunar and can be mounted.
Thunar File Manager on Xubuntu did not display the options of Extract or Extract Here... when right clicking on an archive file. This was because the thunar-archive-plugin is not installed. To get the option to extract archive files, open a terminal window and install the thunar-archive-plugin as below: $ sudo apt-get install thunar-archive-plugin <enter>