CHT seems to lookup the default language of a device and sets this language as the default for the form it displays. However, if this language is missing in the form, then only empty strings are displayed.
Second issue I have discovered:
In the ODK documentation, a multilanguage form should have headers defined such as
label::English (en)
But if used in CHT one gets only empty values, the strings are not displayed. One must write
label::en
CHT seems to lookup the default language of a device and sets this language as the default for the form it displays.
Just to clarify, the forms should be displayed in the language selected by the user when logging into the CHT (after opening the app for the first time). However, you are correct that there is an existing issue about the default language handling when the language is not present on the form.
Regarding your second issue around the structure of the label headers in the xlsxform, I have logged a new CHT issue to address this problem with being out of spec.
Feel free to respond here or on the issues with more thoughts/details regarding your particular situations and is problems you are facing here. That can help us when trying to prioritize getting these issues addressed!
@jkuester thank you for this hint.
FYI: one can also make appear the English version when the user changes its language in user settings → edit user profile.