Example page demonstrating how to construct a video grid using "Text with media (columns) + A remote video"
It's possible to use both YouTube & Vimeo embeds, YouTube has better support for generating a thumbnail automatically.
The thumbnail image can be customised if you do not like how it's currently displaying, to do this locate & edit the remote video in the media section here https://nmite.ac.uk/admin/content/media-grid and update the "Preview Thumbnail" with an image of your own
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