I had someone ask recently:
Q: In a multi-language form, is there are metadata/audit fields we can set that records the language the user has selected when submitting the form? I can't see it in XLSForm specs but not sure if there's a sneaky trick.
It looks like “language change” was considered as something to add to the form audit log, but not incorporated yet?
I was wondering if there was way, since jr:choice-name will pull the label for the active language, you could maybe have a hidden question with a single choice that is selected by default, with language names as the labels for the different languages for the one list option. Then use a calculate to pull the label for the active language (which will be the language name) and store that in the data for the submission? Note that I tried and couldn't create this.