As of WordPress 5.8 a new block-based widgets editor has been rolled out. The new Widgets screen (Appearance → Widgets) and Customizer (Appearance → Customize → Widgets) now allows users to add blocks to their widget areas using the familiar block editor interface, which was introduced in WordPress 5.0. Except that only a few users are converted to blocks.
While the new block widget editor gives users powerful new ways to customise their sites using the rich library of core and third party blocks – it doesn’t always work predictably and for users unfamiliar with blocks it may present issues.
The official pages say
Existing widgets and third party widgets will continue to work and can be used alongside blocks.Widget Blocks
Our experience, so far, has been mixed so for now we have elected to offer users the option via a plugin to disable block widgets.
The block-based widgets editor is enabled in WordPress 5.8 by default and is still available on a new site.
Like the Classic Editor, which remains the OurLocality default, you can re-enable the new block behaviour easily by simply deactivating the Classic Widgets plugin.