I have explained in the past that the current income tax is not unconstitutional. The 14th creates a class of people whose citizenship is in the United State [ fed gov ]. This citizenship therefore arises under Art 4 and guess what, alleged violation are prosecuted in an Art 4 court. Congress has always had the power to lay a privilege tax on the exchange of labor for other goods or services for these people.
Therefore, the income tax is not unconstitutional. It is the application that is very often unconstitutional. The courts have long recognized that there are people who are citizens of their state which are in no way tied to the United States / fed gov. There is no constitutional authority to impose such a tax on them. In fact, to do so the gov has to pretend they are citizens via the 14th amendment and that is a crime.
Thus it is unconstitutional to impose the income tax on state-only citizens or to even drag them into an Art 4 USDC for any alleged crime that happens in a state. Thus the tax is constitution but its application on everyone in the state is not.