I still don’t have any persimmons of my own to test (fingers crossed for next fall), but one thing that I see mentioned in research papers on the subject that I haven’t seen explored thoroughly in the hobbyist space is the effect of temperature. I’ll have to find it again, but one source suggested an anoxic environment (I think CO2) at 40c for 2 hours or 60c for one hour to remove astringency. However, if you leave it in too long at 60c, the astringency can come back and not be removable. I’ve also seen some videos from parts of China where they give their persimmons a soak for a couple days, but they start with hot water, so there’s probably something to that. I think submerging persimmons in a cooler with a sous vide circulator would be an easy way to achieve this time and temp combo. I also wonder if American persimmons might respond to treatment at higher temps.
Edit: Found my original post. It’s 5h at 40c or 1/2-1 h at 60c. Going over 2h at 60c permanently sets the tannins.