They're still working on him - https://www.theguardian.com/science/2018/jul/12/otzis-last-supper-mummified-hunters-final-meal-revealed
This (https://honest-food.net/bracken-fern-edible/) may have some bearing on the contents of his stomach.
Bracken cooked in ibex fat may well have been non-poisonous and tolerable to the taste buds.