Vyxal, 3 bytes1 byte
⌐ Same method as DLosc's 3 byte Pip answer. Takes a list of lists of either 0 or 1.
Simply computes 1 - n for each digit. Alternatively,
Vyxal, 3 bytes
₀S* Takes a multiline string of 0s and 1s. The flag, header and footer are for allowing the test cases to be directly pasted in without having to change them.
Explained
₀S* ₀S # The string "10" * # Ring translate the input according to that - change 0 to 1, 1 to 0 and leave newlines as they are.