If a dog’s nonsapience is part of their gender, and anyone pursues a sexual relationship with that dog, then I’m calling that bestiality and urging them to stop, as we’re getting into rape territory. Believe it or not, I’ve been in a similar situation before. However, most dogs don’t consider intelligence part of their identity to the degree that they reject sapience.

So you're saying that they're effectively not dogs in some deep and essential way?

And as to your question, if I were a school principal and a student suffered from species dysphoria that a litterbox would relieve, I would provide that student with a litterbox (in the bathroom, not in the classroom) so long as that student or their family/carer took responsibility for keeping it clean.

Fucking Christ.

Now I urge you to read at least the Research section of this Wikipedia article so you can be acquainted with the science https://en.wikipedia.org/wiki/Otherkin

This is the totality of the 'research' section of wiki:

Daniell Kirby wrote the first academic paper on otherkin in 2008, which served to introduce the community to other academics.[14] Kirby described otherkin as sharing ideas with the neopagan movement, however she called this an "interim classification", and warned that "to construe this group as specifically neo-pagan or techno-pagan obscures the focus of the participants".[14] Subsequent research has treated the otherkin community as having an essentially religious character.[23][16][30][31]

From 2016 onwards, otherkin research has taken more of a narrative identity approach, investigating how otherkin come to understand their experiences.[32][21][4] Reviewing prior research, Stephanie C. Shea criticizes the prevailing conception of the otherkin subculture as being, or being alike to, either a religion or a spirituality.[33]

In four surveys of furries (with a sample size of 4338, 1761, 951 and 1065 respectively), depending on the sample, between 25% and 44% responded that they consider themselves to be "less than 100% human", compared to 7% of a sample of 802 non-furries surveyed at furry conventions.[34]

What am I supposed to glean from this that I didn't already know?

Fuck's sake. Next you'll start talking about your tulpa.