Accessibility Errors in Google Lighthouse
Offscreen content is hidden from assistive technology
If you have content that starts offscreen but appears on click, it needs to be perceived as offscreen by bots and screen readers. You can use CSS:hidden to do this.
Google Lighthouse says
Ensure that only relevant parts of the page are exposed to screen readers and other assistive technologies. For instance, content that's offscreen or just presentational should be hidden from assistive technologies.