Content types missing in Site Pages library "New" dropdown, and not able to create pages

Symptoms

User goes to site pages, clicks the "new" button and only sees "link" and "folder"

Library settings show the site page content type or other content types that were added to the library.

User can still create pages if they go to an existing page and use the new button there, but once a page gets created there is no way to change its content type.

Solution

As a global 365 admin, go to the sharepoing admin site, click Settings > Pages > and then "Allow users to create new modern pages"

 Notes

This should also be a warning for admins who turn this off - it does not actually prevent users from creating modern pages - I was still able to do so using both the "new" button in a page and also using powershell.