the default language takes precedence over the language setting in the browser. In my eyes the default language should only be used if no matching translation is available.
The default language is an optional env var. If you wan't the browser language to take precendence, just leave the DEFAULT_LOCALE env var commented out
It seems to me, that at the moment the browser language setting is never taken into account. According to this line
https://github.com/bigbluebutton/greenlight/blob/d6a28035e8bb817ec5061077a5df9ff7e3c01cb7/app/javascript/contexts/auth/AuthProvider.jsx#L41
the default language takes precedence over the language setting in the browser. In my eyes the default language should only be used if no matching translation is available.