Chrome Canary has started showing a promo bubble under the Media Controls icon that reads “Save an image of the video frame from Media Controls,” with Remind Me Later and Show Me How buttons. Clicking Show Me How points you straight at the Save Video Frame icon in the panel.
The feature itself is not new. Save Video Frame has been in the Global Media Controls panel since the Chrome 121/122 era. What is new here is that Chrome is going out of its way to tell you it exists — which, going by how few people I have ever seen use it, is probably overdue.
Here is what the promo looks like when it appears in the toolbar:

And here is the button it is pointing to, in the Media Controls panel while a YouTube video is playing:

How to use it
Play a video, pause on the frame you want, click the Media Controls icon in the toolbar, then click the Save Video Frame icon at the top right of the card. You get a clean still of the video — no player controls, no overlays, no cropping afterwards. That is the whole point of it over a regular screenshot.
The prompt is showing up in Canary right now, so expect it to reach Stable in a release or two. If it never shows up for you, the button is still there — Chrome just will not have introduced you to it.