This is a great question.
Really the contraindications for dandelion and bitter herbs in general are around potential for gallstones or a blocked bile duct, since their action has the potential to move gall stones somewhere that they don’t want to be. Therefore if a person does not have their gall bladder anymore, there is no worry about this happening.
Without a gallbladder, bile is still being created by the liver and released into the duodenum, just not in a controlled manner. Therefore the effect of dandelion/bitters would mean that there could be a slight increase in the bile being created and released by the liver shortly after taking them. So actually they are still of great benefit in terms of supporting digestive function.
I hope that is of help and bitters are enjoyed. 🙂