I was finally able to revisit this with a legitimate MSAD server setup on Windows Server 2019. After extensive testing I can finally say without a doubt there should be no issues with User/Agent logins with PHP 8.1, v1.17.3, and latest build of LDAP plugin with correct LDAP settings configured.
If you still have issues check to see if you have more than one instance of the LDAP plugin enabled. If so, disable one of the instances and retest. Also, check to make sure your Search User and Search Base is correct. These two settings are very important. You can find the appropriate Search User string by running the following in a command prompt on the domain controller (this is assuming the administrator's username is Administrator):
dsquery user -name "Administrator"
This should give you something like: