The navigation module defines a set of derivative block plugins for each of the defined menus on your Drupal site. These blocks are meant to be used exclusively within the Navigation and not meant to be generally usable as blocks in the rest of your site. However, at present, b/c these are defined as block derivatives, they are leaking into the Block layout UI:
Update code to exclude all navigation_menu block plugin derivatives.
Patch
All navigation-specific blocks should be hidden from the Block layout UI
Active
11.1 🔥
navigation.module