OpenLDAP Invalid credentials for readonly user - openldap

Question

I try to follow this guide https://www.talkingquickly.co.uk/gitea-sso-with-keycloak-openldap-openid-connect to create SSO solution with OpenLDAP and Keycloak. I'm trying to add the readonly user. It should be the same LDIFs as here https://github.com/osixia/docker-openldap/tree/master/image/service/slapd/assets/config/bootstrap/ldif/readonly-user
I apply those LDIFs for the readonly user but I get
$ ldapsearch -x -H ldap://localhost:1389 -b "dc=muellerpublic,dc=de" -D "cn=readonly,dc=muellerpublic,dc=de" "+" -w xxx
Handling connection for 1389
ldap_bind: Invalid credentials (49)
Here are the users/groups:
$ ldapsearch -x -H ldap://localhost:1389 -b "dc=muellerpublic,dc=de" -D "cn=admin,dc=muellerpublic,dc=de" "+" -w xxx
Handling connection for 1389
# extended LDIF
#
# LDAPv3
# base <dc=muellerpublic,dc=de> with scope subtree
# filter: (objectclass=*)
# requesting: +
#
# muellerpublic.de
dn: dc=muellerpublic,dc=de
structuralObjectClass: organization
entryUUID: ce600638-0d8f-103c-8fb1-1558d46de393
creatorsName: cn=admin,dc=muellerpublic,dc=de
createTimestamp: 20220119162257Z
entryCSN: 20220119162257.152328Z#000000#000#000000
modifiersName: cn=admin,dc=muellerpublic,dc=de
modifyTimestamp: 20220119162257Z
entryDN: dc=muellerpublic,dc=de
subschemaSubentry: cn=Subschema
hasSubordinates: TRUE
# users, muellerpublic.de
dn: ou=users,dc=muellerpublic,dc=de
structuralObjectClass: organizationalUnit
entryUUID: ce601dc6-0d8f-103c-8fb2-1558d46de393
creatorsName: cn=admin,dc=muellerpublic,dc=de
createTimestamp: 20220119162257Z
entryCSN: 20220119162257.152933Z#000000#000#000000
modifiersName: cn=admin,dc=muellerpublic,dc=de
modifyTimestamp: 20220119162257Z
entryDN: ou=users,dc=muellerpublic,dc=de
subschemaSubentry: cn=Subschema
hasSubordinates: FALSE
# readonly, muellerpublic.de
dn: cn=readonly,dc=muellerpublic,dc=de
structuralObjectClass: organizationalRole
entryUUID: ce60b6a0-0d8f-103c-8fb3-1558d46de393
creatorsName: cn=admin,dc=muellerpublic,dc=de
createTimestamp: 20220119162257Z
entryCSN: 20220119162257.156845Z#000000#000#000000
modifiersName: cn=admin,dc=muellerpublic,dc=de
modifyTimestamp: 20220119162257Z
entryDN: cn=readonly,dc=muellerpublic,dc=de
subschemaSubentry: cn=Subschema
hasSubordinates: FALSE
Here are the LDIFs created:
20-readonly-user.ldif: |
# Paths
dn: cn=readonly,dc=muellerpublic,dc=de
changetype: add
cn: readonly
objectClass: simpleSecurityObject
objectClass: organizationalRole
userPassword: {SSHA}5Y0mPhzRCYDBRltdvF6hp+m0DWgPTdjD
description: LDAP read only user
21-readonly-user-acl.config.ldif: |
dn: olcDatabase={2}mdb,cn=config
changetype: modify
replace: olcAccess
olcAccess: to * by dn.exact=gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth manage by * break
olcAccess: to attrs=userPassword,shadowLastChange by self write by dn="cn=admin,dc=muellerpublic,dc=de" write by anonymous auth by * none
olcAccess: to * by self read by dn="cn=admin,dc=muellerpublic,dc=de" write by dn="cn=readonly,dc=muellerpublic,dc=de" read by * none