WordPress added a lazy-loading feature enabled by default in the 5.5 release.
There are a number of solid plugin options for WordPress and those plugins include additional features like image optimization and free CDN integration.
The Lazy Loader plugin includes a number of lazy loading options for image and video assets on your site. After you have installed and activated the plugin the settings for it can be managed from;
Settings > Media
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Lazy loading image assets on your sites is an easy way to improve site load times for site users without a lot of work to get it working correctly.