helpgeek

By default, the built-in Recent Posts widget in WordPress only allows you to 
display up to 15 recent posts max, even if you specify a larger number. This 
is hard-coded into the WordPress core so any modifications you make would have 
to be redone upon every WordPress update.
No longer!
The Recent Posts Widget Unlimited functions exactly as the built-in WordPress 
widget but without the 15-post restriction. You can now specify an unlimited 
number of recent posts to display without resorting to modifying the WordPress 
core.

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.
<blockquote>
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).
</blockquote>

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.

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