Gargron

Displays authors of a collaboration post in place where only one is shown by default. Uses custom fields (key=<code>coauthor</code>;value=user’s username; one per user). Note: If it doesn’t automatically display the co-authors you must manually add <code>if(function_exists(wt_the_coauthors_link)): wt_the_coauthors_link(); endif;</code> into your theme (in PHP <code><?php ?></code> brackets, of course).

WT Co-authors

Using WordPress Custom Fields, and without editing any template files, lets you credit all authors on collaboration posts.

Romulo Vieira

Restrict on which categories a user can post.
It also blocks the users from creating/editing/deleting categories.
Only Admins can set other user’s categories.
Works with Block Editor and Classic Editor.
It’s compatible with IE11.

Restrict Author Categories

Restrict on which categories a user can post. Just that!

WT Co-authors vs Restrict Author Categories