How do I recommend a student requiring extended deadlines?
You were already required to evaluate this student's work under the assumption that they performed under the same circumstances as everyone else, so why suddenly stop doing so at a recommendation letter?

That said, this quickly becomes a legal matter, and we have few true legal experts (for any jurisdiction) on this site.  I'm certainly not one of them, but here's my opinion and understanding...

The companies are not allowed to discriminate based on disabilities, and are required to make "reasonable accommodations" for them.  As such you can reasonably assume that whatever job is being applied for will already have this in effect, and that the disability is therefore irrelevant.

If, for some reason, the student is hiding their disability from potential employers&mdash;or, worse, had been faking it with the University&mdash;, then that is their responsibility, and the responsibilities of whatever (medical) professionals were involved in the evaluation, not yours.

If you remain in doubt&mdash;it would not be unreasonable to be confused on whether certain things you know about the student fall under "protected disability concerns" versus "legitimate, non-protected concerns"&mdash;, contact the very office that handles these disability arrangements, and possibly arrange to have a meeting where you can discuss these matters at length.  They should be able to provide you with guidance on how to faithfully execute your duties vis a vis recommendations while remaining in compliance.  You can even contact a lawyer for yourself, though you will likely have to pay for this.  The disabilities office will be inclined to advise you to act in whatever is most convenient for them and the university, which may be more strict than is legally required and enforceable, but in a case like this I would suggest you follow that because of:

The golden rule of writing a recommendation letter is: if you feel you cannot write a good recommendation letter for the student then reject their request to write one, and if you feel you cannot write a strong one then tell them so, so that they can decide if that is acceptable or not.

If you feel that these will automatically apply to you with respect to students with disabilities, you may want to (preemptively) arrange to speak with someone in the disabilities office, or a personal lawyer (this may be more strongly advisable in this situation), about writing letters for students with disabilities.  This would be to head off any potential concerns about you acting discriminatingly towards such students.