I allowed a no-name, heirloom, oblong, astringent variety to become soft, before peeling and dehydrated them, for a naturally-sugary treat. Air layers grow cauliflower-like, yellow callouses, but have never once rooted for me. Very-rare seeds (maybe 1 seed for every 3 dozen fruit) had a high germ rate.
Black sapote, a persimmon, responded very well to bat guano. Grafting may confer cold tolerance.
And, African ebony, also a persimmon, are germinating in water. These apparently send out suckers from the roots, so may be a source of income.
1+ ounces of free date plum seeds have yet to germinate, after one year, in common soil.