Comment 7 for bug 1905105

Follow these instructions, and this should remedy your problem...

(1)

$ sudo dpkg-reconfigure locales

    Use <Page Up>, <Page Down>, <Up Arrow>, <Down Arrow> to navigate lists.
    Use <Space Bar> to select or unselect list items.
    Use <Tab> to switch between lists and buttons.
    Use <Left Arrow>, <Right Arrow> to switch between buttons.
    Use <Enter> to "Click" a selected Button.

(2)

On the 1st page "choose which locales to generate":

    Press the <Space Bar> to select "en_CA.UTF-8 UTF-8"
    Press the <Space Bar> to **UNSELECT** en_"CA ISO-8859-1"
    Continue to page through the list and ensure everything else is **Unselect**.

        [ ] en_CA ISO-8859-1
        [*] en_CA.UTF-8 UTF-8
        [ ] en_US.UTF-8 UTF-8

    (You may be able to select other locales, but do not select anything that doesn't say "UTF-8").

    Select "OK" to go to the next page.

(3)

On the 2nd page, "select the default language for the entire system":

    Scroll down and select "en_CA.UTF-8"

        en_CA.UTF-8

    (You can only select one default locale; make sure it says "UTF-8").

    Select "OK" to go to the next page.

(4)

You will see the following output:

    sxubuntu@xubuntu:~$ sudo dpkg-reconfigure locales
    Generating locales (this might take a while)...
    bn_BD.UTF-8... done
    .
    .
    .
    zh_SG.UTF-8... done
    Generation complete.

(5)

Reboot (or Logout / Login)

(6)

Reinstall Cubic (just to make sure it is a clean install).

    $ sudo apt autoremove --purge cubic
    $ sudo apt-add-repository --remove ppa:cubic-wizard/release
    $ sudo apt-add-repository --remove ppa:cubic-wizard/classic

    $ sudo apt-add-repository ppa:cubic-wizard/release
    $ sudo apt update
    $ sudo apt install cubic