Widgets section no longer under appearance

Did you recently change to a new Block Theme? https://ww.wp.xz.cn/support/article/block-themes/

If so, you’re using the new Site Editor https://ww.wp.xz.cn/support/article/site-editor/, and the widget areas are now Templates: https://ww.wp.xz.cn/support/article/template-editor/

If you have not recently changed your theme, this problem may be a plugin or theme conflict. Please attempt to disable all plugins and switch to the default Twenty Twenty-One theme. If the problem goes away, enable them one by one to identify the source of the problem.

If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you while you’re still logged in without affecting normal visitors to your site.