<video> elements do not contain a <track> element with [kind="captions"]
Webflow allows video to be embedded from YouTube, Vimeo or through the Embedly plugin. It's important to give captions with your YouTube or other videos .
On YouTube you can add automatic captions, but it's better to use the Transcribe app.
Google Lighthouse says
Captions make video elements usable for deaf or hearing-impaired users, providing critical information such as who is talking, what they're saying, and other non-speech information.