Migrate local to simple LDAP: issue login with username

I am migrating my Gitea instance from local auth to simple LDAP.
After configuring everything following the doc, I try to login with the LDAP username and password and I get this error in the logs:

www-gitea-server-1  | 2023/09/11 12:10:39 ...vices/auth/signin.go:115:UserSignIn() [W] Failed to login 'cretin' via 'LDAP': e-mail already in use [email: <my email>]
www-gitea-server-1  | 2023/09/11 12:10:39 .../context_response.go:74:HTML() [D] Template: user/auth/signin
www-gitea-server-1  | 2023/09/11 12:10:39 ...ers/web/auth/auth.go:206:SignInPost() [I] Failed authentication attempt for cretin from 192.168.80.1:49638: user does not exist [uid: 0, name: cretin, keyid: 0]
www-gitea-server-1  | 2023/09/11 12:10:39 ...eb/routing/logger.go:102:func1() [I] router: completed POST /user/login for 192.168.80.1:49638, 200 OK in 2497.6ms @ auth/auth.go:170(auth.SignInPost)

Yet, when I do the same bu instead I use the email instead of username, it works.

I changed the “Authentication Source” to “My LDAP” and set the LDAP username in the “Authentication Sign-In Name” form of the user.

The “User Filter” is:
(&(objectClass=posixAccount)(|(uid=%[1]s)(mail=%[1]s)))

What did I miss?