Just stumbled across this, I haven’t tried it yet as I have swapped my Theta S for a Xiaomi. If you try it please let me know if it’s any good or not.
HDR Photo app for Ricoh Theta cameras allows you to capture multiple images with different exposures, ISO, and shutter time (bracketing). The images can then be stitched into a single HDR (High Dynamic Range).
Head over to tequnique.com to find the full range.