Is it considered disobedience or a sin to agree to connect a deceased father to feeding, oxygen, and treatment against his will, if the aim of that is to help him?

It is not permissible to force a sick person to consume food and drink that they do not desire, based on the Prophet's (peace be upon him) saying: "Do not compel your sick ones to eat, for indeed Allah feeds them and gives them drink." An exception to this is when there is a fear for their demise if they do not consume food; in such a case, they should be given what suits their condition, based on the opinion of doctors. As for compelling a sick person to take medicine, the general principle is that it is not recommended, unless there is a fear of their demise by abandoning it, in which case it is permissible to compel them. Therefore, there is no harm in allowing your father to be given food and medicine forcefully to save his life, and this is not considered an act of disobedience to parents. And among the acts of filial piety towards a parent after their death are supplication, seeking forgiveness for them, and giving charity on their behalf.