You can enable audit logs on the domain controller and check for that type of information. The audit logs include AccountLogon and LogonLogoff and show the user attempts to access a particular computer.
The security audit logs should show you these types of events. There's nothing LDAP specific there but they should give you what you're looking for. https://learn.microsoft.com/en-us/azure/active-directory-domain-services/security-audit-events
If you don't see these there may be an issue with your LDAP connection and I would suggest opening a support ticket.
https://learn.microsoft.com/en-us/azure/active-directory-domain-services/security-audit-events