Here is a CSS only snippet to add that fancy skeleton screen gleam loading animation to your card UI inspired content blocks. You have multiple variations from light mode, dark mode and light mode with a grey background and also ones with high contrast options.
If you are having trouble with the pen, try the archived copy on GitHub
CSS Skeleton Screen Snippet
See the Pen Skeleton Screens by Aimee (@aimeeotsu) on CodePen.0