If you're not reading primary sources, I don't know what to say. the 14th amendment only has 5 sections, none of which are about banning slavery. They are there to make sure that states can't disenfranchise people based on who their parents are.

But for your benefit: https://constitution.congress.gov/constitution/amendment-14/

> which involves an ancillary aspect of the 14th amendment?

SECTION 1:

All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

Its 25% of the entire amendment. Its not ancillary. The point of it was to allow the emancipated slaves to actually have citizenship. Otherwise not only would they have not been able to vote in the states that they were born in, neither would their kids, as their children would not have been US citizens.