When you open Instagram, videos will still autoplay with the sound off. But if you tap to turn one video’s sound on, indicated with a speaker icon in the bottom left, all other videos will autoplay with sound too for the rest of your Instagram session. You can still tap to toggle a video and all subsequent ones back to silent. And when you close the app, the autoplay audio resets to off for next time you use Instagram. So basically, Instagram still defaults to audio off when opened, but applies your last toggle on or off for the rest of your session.
