Am I legally obligated to change my current lineage and affiliate myself with my biological mother, knowing that this could lead to legal penalties for my adoptive parents, or does averting legal harm from them negate this religious obligation for me? Do I have duties towards my biological mother, and am I required to search for her?

It is forbidden to attribute oneself to other than one's real father, knowing this, because Allah the Almighty says: "Call them by [the names of] their fathers; it is more just in the sight of Allah." This is due to the consequences that follow, such as inheritance and mahramiyyah (unmarriageability). There is no sin upon you for what has occurred, but it is necessary for you to change the name and attribute yourself to your real mother or to a general name, unless the change is impossible or would result in harm. In that case, you are not required to change it, but you must make your real lineage known among those around you to prevent the mixing of lineages and rulings. You must search for your mother and honor her, while showing gratitude and kindness to those who raised you.