I found an error in the search, so you were definitely right (the username wasn't listed under uid). I was thrown off as the CLI tool ldapsearch found my user use the base DN but bin/auth gave a PHP error so I thought this was a code problem not just a failed login and the

bin/auth ldap --trace

[2] <connect> phabricator_auth

<<< [2] <connect> 1,065 us

[3] <query> SELECT * FROM auth_providerconfig ORDER BY id DESC

<<< [3] <query> 355 us
Enter LDAP Credentials