I had the same problem.
The column "api_key" is not created in "user_field_data". I realised it when I tried to create a key for a user.
I tried to uninstall the module, but it wasn't possible because of the problem discussed in
https://www.drupal.org/project/key_auth/issues/3203785
🐛
api_key field isn't found in users_field_data table
Needs work
The site got broken with an error:
TypeError: in_array(): Argument #2 ($haystack) must be of type array, null given in in_array() (line 70 of modules/contrib/key_auth/src/KeyAuth.php)
The only way to uninstall the module and make the site work again was to create that column manually.
Hi, I am interested as well in this module for a blog. I am now relaying on an external service but it would be great to keep all the users db inside Drupal. Is there any chance that this can be updated to simplenews 4? I can't bring very much, I can't write in PHP, but I can help with translations and documentation if it is needed.