The block settings "gear" button doesn't appear on Layout Builder layout settings pages

On Layout Builder layout editing pages (for example, on /admin/structure/types/manage/page/display/default/layout page), if the “Show content preview” checkbox is turned off, the gear icon (context menu button) does not appear when hovering over a block.

Workaround:
Check the “Show content preview” checkbox.
OR Remove "display: none" from block__inner div.
OR Switch to another theme.

Some blocks still don't show the context menu.
Then you need to copy the url of any other block and paste the UUID of this block into it.