The constitution never said to count the people who vote. If you wanted to know that, just count how many people vote.

The constitution also doesn't preclude counting who is able to vote. The constitution places limits on the government, but we can add things that act within those bounds. Asking about citizenship falls within those bounds.

Article 1 Clause 3 requires enumeration of all free persons.

Yes. Again, counting citizens does not also preclude counting free persons. We already gather data on peoples race and religion, proving that we can gather more data than just headcount, and citizenship information has already been gathered between 1950 and 2000.

Counting only citizens does preclude counting all free persons. (If you're speaking about counting all but considering citizenship a demographic, that's legal and used to be done iirc, but was dropped as it was feared it would disincentivize non-citizen being counted. The recent court case about the citizenship question was settled by the courts because of administrative procedure, not the legality of the question.)

Moreover, collecting demographics data is orthogonal and I'm not sure why you're bringing it up.

The constitution specifically says the census is a count of all "free Persons", not only citizens. Obviously SCOTUS will weigh in now, but I think it's important to realize the actual wording of what the census is.

14th amendment drops the "free"

While also striking the 3/5 compromise, so I don't think it changes the reading.

It uses the term "free Persons" but the context is "their respective Numbers, which shall be determined by adding to the whole number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons".

So "all other Persons", i.e. slaves, were counted.

Well, the 3/5 compromise has been removed, but even still are you arguing that immigrants aren't people or aren't free, i.e. not slaves.

Prisoners aren't free, but they still use infrastructure and I'm pretty sure they are supposed to be counted in the census.

They are, because they are free in that they are not slaves. Prisoners still have a plethora of constitutional rights.

The amendment against slavery excludes prisoners: Sometimes, they are, indeed, slaves.

And yeah, they have rights. But they don't have the right to freedom as we know it nor do they have the right not to be slaves.

You act as though there is a single freedom, which is not the case by any means. The amendment carves out specific exemptions for prisoners for certain things, but that doesn't make them chattal slaves, nor does it remove the rest of their rights, e.g. cruel and unusual punishment, ability to have representation, or have their speech curtailed.

I'm not sure who would classify prisoners as free, though. Classifying prisoners as free is warping what most folks would consider free. You can have rights and not be free. POW's are supposed to have certain rights, too, but that's hardly free. You can have rights without being free. Not being chattal slaves doesn't make you free either, nor does it mean you aren't a temporary slave.

In general, folks would agree that if you are in a situation where you are forced to eat at certain times, possibly only use toilets or showers at certain times, can be used as labor with little to no pay, and can never roam freely at the behest of armed guards that can shoot you, you aren't free. The main exception to some of this is military, but for now, this is something folks choose and some countries' soldiers are more free than the ones in the states.

I'm not going to continue this discussion as you're unwilling to understand that we're discussing free vs non-free as in non-chattel-slave vs chattel-slave, a.k.a. the ownership of another human being. The state does not own prisoners. Prisoners continue to have a plethora of constitutionally protected rights. Prisoners are counted in the census.

Your interpretation would imply they intended non-citizen native Americans to be counted in the Census.

The original text and the 14th amendment both excluded untaxed indians from the apportionment for the house of representatives.

So, they could ask to be counted, but there is no mandate to count them.