There are multiple formats that subtitles can be delivered in - the older boxes don't support the format that Now TV and discovery+ plus use.
Edit: if Now TV now have subtitles on the older boxes then great. Sounds like they've found a way to either convert them or display them themselves (I'll update the delivery manager - he's the one who confirmed the discovery+ position to me earlier today). It's taken discovery+ 9 months to get the app working as it is ... I wouldn't hold out much hope on getting subtitles any time soon.
