The Facebook post shared story video narration is in a non-English language, for which English captions are available but not supported by Facebook when the post shared story is launched from Facebook, so instead one must run the shared story link in a separate standalone browser like Safari/Firefox/Chrome. Hence, for English captions, paste the shared story link just copied from the Facebook post into a separate standalone browser to get to a site typically displaying a video with an overlaid Play control; if not in YouTube, touch Play control to view, otherwise next touch/click the video anywhere outside the Play control to display the popup controls panel, then select the gear icon, verify “Captions English” selected, wait until after popup clears, then touch/click Play control (can take ~ 5-10 seconds before playback begins; captions may not display in landscape/full-screen mode).
¹ For other languages replace the word “English” with the other language name everywhere above.