Tabs created with hook_menu_local_tasks_alter() don't display to non-admins

The tabs are made to be used as local tasks for admins...
So 'im prety confident this is by design.
Will verify later.

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Brad, i don't know if you know panels or not but you can do what you're trying to do with panels using context to set the tabs. Its kind of a similar way you'd create tabs using the views modules and specifing paths like careers, careers/benefits, etc... but with panels you can actually go a little deeper and specify certain node/add/edit forms, specific nodes, etc... to build your tabs.
The context module may do something similar but i'm not as experienced with that one. Otherwise, perhaps you're looking for a way to just code it yourself.

Could we have some more conversation about this, I think either the documentation on the page needs to be changed for the hook in the API docs or this should be allowed.

Adding a access callback much like other menu systems would make sense and I feel like this is a feature that could be used for other means than just administrative tasks.

Thanks!

This seems like a bug to me. These tabs have been used for non-administrative links for ages. The user/register and user/login pages are prime examples of this. It also seems kinda crazy to have to use hook_menu() to add tabs for existing pages, especially nodes.

I was able to get this working by manually updating the $data['tabs'][0]['count'] value. Even when new tabs are added the count is never updated after being altered, which results in no tabs displaying despite the fact that the data is there. It's possible I'm doing something wrong in my implementation, since developer is not my primary role, but I don't know...

The code I'm using is here and is in use on this page. You can reproduce by taking the following steps:

1. Enable the module in the gist.
2. Enable the contact module and set permissions for anon users to access it.
3. Add a node and change the paths in the module to point to one in your DB.
4. Comment out lines 61-63 and log out.

You'll notice that the tabs will appear on the contact page (where an existing menu item already exists and is just altered), and no tabs will appear on the node (because there are no tabs normally). Then enable the last few lines, clear the cache and the tabs will work as expected.

Hope it helps someone.

@bradjones It's not a patch because don't have the solution. It's a custom module with a few lines of code at the bottom that hacks in a fix. I'm not even positive that it is a bug. I posted it to better describe the issue so that someone who is able to can easily grab the code to test with and maybe add use it for unit tests.

This worked for me to show Drupal-provided tabs (e.g. node view/edit/delete/etc), I do not have any custom tasks that need to be displayed.

In the Block Layout (admin/structure/block; make sure you're editing the desired theme), there is a block for Tabs. Configuration for this block seems to have a default visibility restriction by Role, set to Administrator. You can add any additional roles you want to see the block, or alternatively (like I did) uncheck the Administrator role to not restrict the visibility by role.

This works as designed in D8+

Taking this example:

/**
 * Implements hook_menu_local_tasks_alter().
 */
function MYMODULE_menu_local_tasks_alter(array &$data, string $route_name, CacheableMetadata $cacheability): void {
  $data['tabs'][0]['user.page'] = [
    '#theme' => 'menu_local_task',
    '#link' => [
      'title' => t('My account'),
      'url' => Url::fromRoute('user.page'),
      'localized_options' => [
        'attributes' => [
          'title' => t('Add content'),
        ],
      ],
    ],
  ];
}

It shows for anon users when viewing a node