<frame> or <iframe> elements do not have a title
Give your iframes a <title>
One of the most frustrating things about Google Lighthouse is when it flags an error on one of its own products.
YouTube videos embedded in Webflow will always fail because they do not have a <title>.
Vimeo supplies a title, so you get your Lighthouse points, but it's <title="Vimeo embed>, which isn't very helpful.
You can avoid this Lighthouse error by using the generic Webflow embed element. Copy the Embed code from Youtube and put it in the embed element in Webflow. Then and add a title="your_video_title" .
Google Lighthouse says
Users of screen readers and other assistive technologies rely on titles to describe the contents of frames. Navigating through frames and inline frames can quickly become difficult and confusing for assistive technology users if the frames do not have a title attribute.