I would vote for extracting a sub-component for one question-answer block and handle the expanded-state in there. This will also fix the code duplication in your code.

import styles from '../styles/FAQs.module.css'
import {useState} from 'react';

const FAQ = ({question = "", answer = ""}) => {
    const [isToggled, setIsToggled] = useState(false);

    const onToggle = () => {
        isToggled ? setIsToggled(false) : setIsToggled(true);
    }

    return <div className={styles.accordionItem}>
        <button id="accordion-button-1" aria-expanded={isToggled} onClick={onToggle}>
            <span className={styles.accordionTitle}>{question}</span>
            <span className={styles.icon} aria-hidden="true"></span>
        </button>
        <div className={styles.accordionContent}>
            <p>{answer}</p>
        </div>
    </div>
}

export default FAQ

import styles from '../styles/FAQs.module.css'
import FAQ from "./FAQ.js"

const FAQs = () =>
    <div class={styles.container}>
        <div class={styles.accordion}>
            <FAQ key="faq-1" question={"Why is the moon sometimes out during the day?"}
                 answer={"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor " +
                     "incididunt ut labore et dolore magna aliqua. Elementum sagittis vitae et leo duis ut. " +
                     "Ut tortor pretium viverra suspendisse potenti."}/>
            <FAQ key="faq-2" question={"Why is the sun sometimes out during the night?"}
                 answer={"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor " +
                     "incididunt ut labore et dolore magna aliqua. Elementum sagittis vitae et leo duis ut. " +
                     "Ut tortor pretium viverra suspendisse potenti."}/>
        </div>
    </div>

export default FAQs

Duplicated code fragments in your JSX are usually a signal that you should extract them. In your case, extraction also fixes the bug as each FAQ gets its own state. It will furthermore help you to prevent issues due to copy and paste mistakes.

In another improvement, you could have the questions and answers in an array and iterate over them in the JSX of the FAQs component. With that, you could separate data from rendering.

The problem with your code is that you have multiple FAQs but you only have one state and one function to handle all the FAQs so when you click on one FAQ, all the FAQs will be triggered because you've one state for all of them.

So create an individual state for all the FAQs.

import styles from '../styles/FAQs.module.css'
import {useRef, useEffect, useState} from 'react';

const FAQs = () => {
  const [isToggled1, setIsToggled1] = useState(false);
  const [isToggled2, setIsToggled2] = useState(false);


  const toggler1 = () => {
    isToggled1 ? setIsToggled1(false) : setIsToggled1(true);
  }

  const toggler2 = () => {
    isToggled2 ? setIsToggled2(false) : setIsToggled2(true);
  }

  return (
    <div class={styles.container}>
      <div class={styles.accordion}>
        <div class={styles.accordionItem}>
          <button id="accordion-button-1" aria-expanded={isToggled1} onClick={toggler1}>
            <span class={styles.accordionTitle}>Why is the moon sometimes out during the day?</span>
            <span class={styles.icon} aria-hidden="true"></span>
          </button>
          <div class={styles.accordionContent}>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
              incididunt ut labore et dolore magna aliqua. Elementum sagittis vitae et leo duis ut.
              Ut tortor pretium viverra suspendisse potenti.
            </p>
          </div>
        </div>

        <div class={styles.accordionItem}>
          <button id="accordion-button-1" aria-expanded={isToggled2} onClick={toggler2}>
            <span class={styles.accordionTitle}>Why is the moon sometimes out during the day?</span>
            <span class={styles.icon} aria-hidden="true"></span>
          </button>
          <div class={styles.accordionContent}>
            <p>
              Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
              incididunt ut labore et dolore magna aliqua. Elementum sagittis vitae et leo duis ut.
              Ut tortor pretium viverra suspendisse potenti.
            </p>
          </div>
        </div>
      </div>
    </div>
  )
}

export default FAQs

You need to store toggle status for all the sections/accordions separately in a map/object or an array or multiple state variables and toggle the one that is clicked on.

import styles from '../styles/FAQs.module.css'
import {useRef, useEffect, useState} from 'react';

const FAQs = () => {
const [accordionStatus, setAccordionStatus] = useState({ accordion1: false, accordion2: false });

const toggler = (name) => {
  setAccordionStatus({ ...accordionStatus, [name]: !accordionStatus[name]);
}

   return (
<div class={styles.container}>
  <div class={styles.accordion}>
    <div class={styles.accordionItem}>
      <button id="accordion-button-1" aria-expanded={accordionStatus.accordion1} onClick={() => toggler(accordion1)}>
        <span class={styles.accordionTitle}>Why is the moon sometimes out during the day?</span>
        <span class={styles.icon} aria-hidden="true"></span>
      </button>
      <div class={styles.accordionContent}>
        <p>
          Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
          incididunt ut labore et dolore magna aliqua. Elementum sagittis vitae et leo duis ut.
          Ut tortor pretium viverra suspendisse potenti.
        </p>
      </div>
    </div>

    <div class={styles.accordionItem}>
      <button id="accordion-button-1" aria-expanded={accordionStatus.accordion2} onClick={() => toggler(accordion2)>
        <span class={styles.accordionTitle}>Why is the moon sometimes out during the day?</span>
        <span class={styles.icon} aria-hidden="true"></span>
      </button>
      <div class={styles.accordionContent}>
        <p>
          Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
          incididunt ut labore et dolore magna aliqua. Elementum sagittis vitae et leo duis ut.
          Ut tortor pretium viverra suspendisse potenti.
        </p>
      </div>
    </div>
  </div>
</div>
 )}

export default FAQs