linux4me2

This widget allows you to insert arbitrary Text and/or HTML code (optional) to precede a list of recent posts by category. It makes it easy to add introductory comments and to achieve interesting effects like wrapping your posts list around an image. It’s designed to be lightweight and easy on resources.
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Note: Widget Blocks, added in WordPress 5.8, make this plugin no longer necessary. The same results can be obtained by using a Widget Group, Heading Block, Custom HTML Block, and the Latest Posts Block. The latter also allows the use of multiple categories, which is not available with this plugin. Unless something major happens to change things, I won’t be developing the plugin beyond the current version (2.0.0).
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HTML Plus Recent Posts by Category Widget

Like the Legacy Recent Posts widget, but adds the ability to select the category and add text or HTML before the list of posts.

javierjara

This plugin adds a simple widget that you can customize easily it allows you to display a number of recent blog posts from a specific category. You have the options to choose a title, category, number of posts and whether or not to show the post date or to show the image featured (Post Thumbnails).The posts will be ordered by date just like the default Recent Posts widget included with WordPress. 
check the category you want to show.

Custom Recent Posts Widget Plus

Nice widget it is like the default Recent Posts widget except you can choose a category and in addition show the thumbnails.

HTML Plus Recent Posts by Category Widget vs Custom Recent Posts Widget Plus