Site creation fails when there are certain special characters (at least ampersand “&” seems to be one of those characters, might be others as well) in the admin password defined during the setup process. I believe the characters should be escaped properly (by Local) to allow the use of strong passwords as they are completely valid when setting up a WP site normally outside Local automatic setup.
You can finish the setup after the error message by going to your .local URL and continuing the setup manually. You can even use the same Local-breaking password you first used when trying to set up the site and WP will have no problem using it.
- Add a new site
- When asked, insert an admin password with special characters like ampersand (&), possibly also single quote (’) and backtick (`)
- Windows 10 21H2 (19044.1766)
- nginx, PHP 7.4.1, MySQL 8.0.16
- Local 6.4.0+5927 (but this has been a bug for quite some time now)