Media library doesn't require alt text for new media entities because of the UI flow.
TBC
After selecting the media entity, the user stays in the "Edit Entity" dialog window so that they can complete required alt text and other required fields.
* After selecting the media entity, user gets redirected back to the content edit page
* User then has to then click the "Edit" button to add the required alt text for the image.
* If you skip this step and Save the content, the image will be saved without the required alt text.
* This makes the Media widget not accessible because alt text is required for images and multimedia per WCAG 1.1.1 Non-text Content (see https://www.w3.org/TR/UNDERSTANDING-WCAG20/text-equiv-all.html)
* Once user clicks "Select image" button to add new media, they get redirected to the "Edit entity" dialog window with the entity's details including the required "Alternative text" field.
* They can't save the image without completing the required "Alternative text" field and other required fields, solving the issue.
* Create patch from proposed resolution
* Commit
Select Media
Add New Image
Content Edit
Edit Entity Without Alt Text
Edit Entity With Alt Text
Select Media
Add New Image
Edit Entity Without Alt Text
Edit Entity With Alt Text
Content Edit
Active
2.0
User interface
Makes Drupal easier to use. Preferred over UX, D7UX, etc.
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
Still no clear way to expose the alt text using the Entity Browser when selecting from available assets. Current solution is to provide help text for how to click "edit" after selecting the image to add alt text.