generating post slug with info other than post title

I’m trying to set up a directory of people using custom post types and taxonomies.

I’ve removed support for the title for the custom post type because I just want the user’s display name to act as the title. Additionally, the user is limited to creating just 1 post of that type.

The title is no problem, and easy enough for me to change in the template.

However, upon publishing, the slug generated is something like “auto-draft-1” making the URL look like “https://localhost/mysite/mycustomposttype/auto-draft-1/”

I’m trying to get it to be “https://localhost/mysite/mycustomposttype/username/” or “https://localhost/mysite/mycustomposttype/display-name/”

I see that the slug generation happens upon publishing the post so I’ve looked into the wp_unique_post_slug function in wp-includes/post.php, lines 2800-2857, to see how it works but I’m out my depth here.

Can anyone point me in the right direction?