Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

Treat most indefinite pronouns as singular
Make subjects and verbs agree
Grammar

Indefinite pronouns, those that do not refer to specific persons or things, are singular.

Many of these words appear to have plural meanings, and they are often treated as plural in casual speech. In formal written English, however, they are nearly always treated as singular.

A few indefinite pronouns (all, any, none, some) may be singular or plural depending on the noun or pronoun they refer to.

NOTE: When the meaning of none is emphatically “not one,” none may be treated as singular: None [meaning “Not one”] of the eggs was broken. Using not one instead is sometimes clearer: Not one of the eggs was broken.