The tube is only inserted during feeding.

I have not actually seen it (and I'm not the OP), but I have been told by French farmers that geese do willingly and even eagerly run up to get the tube inserted so that they can have the food force fed into their gullet. At least with the few farmers I've talked to about this, the tube was not inserted permanently (these were very small operations). Having never actually seen it, I don't have any understanding of the discomfort the animals face or the extent to which these reports are true. But neither do I have reliable information that it is not true.

Disclaimer: I don't eat foie gras and don't advocate it either.

The actual fact that geese can eat that much and double size (or more) is natural and necessary for their migration. It's possible to make foie gras by just letting the goose eating itself. Acording to my parents when they were living on farms when young, that's the way they were doing it.

Just banning the practice of force feeding would make more sense.

You can find a few things online about those alternative way https://text.npr.org/s.php?sId=487088946

>The animals are literally force fed with a tube

You don't have to buy the force fed kind though.

This is a by-product of battery breeding, and not the only way to make foie gras. Geese will feed too much anyways at certain times of the year in their own will. Same as pigs that get removed from their mothers and live in cages barely sized for them. It doesn't have to be that way.

Buying responsibly is a first step, and forbidding torturous practises would be another one. Not killing animals at all is yet another discussion.

That's only one way to do it, probably the most efficient one for mass farming. In my country there is a similar delicacy, but instead of tube traditionally geese were fed by hand. Farmers would prepare balls of food, and then those balls were pushed into the geese's beak and down the throat by hand, until it's totally full. This is more time consuming than using a funnel and a tube to just pour the food.