In the most recent AGOL release, Instant Apps added the ability to translate the configurable strings into multiple languages. This is GREAT!
but....
Most (all?) of the apps display feature data based on the popup configuration which isn't translate-able in the app configuration.
My datasets already have fields with data values stored in each of the languages I must support for public-facing apps. Currently I build popups in Arcade that contain formatted sections of information in each language, or I use that one dataset in multiple language-specific maps and apps.
If Arcade included the ability to detect the browser locale, I would be able to simplify the end-user experience by only returning the values in the user's language of choice and reduce the number of functionally redundant maps and I apps I need to maintain.