Hi @Eliot Chen ,
I understand that you are looking for a way to programmatically verify if a user account is locked out via Smart Lockout. While there is not quite an Azure equivalent to the on premises "LockedOut" property, you can check the AccountEnabled or BlockCredential status in Azure AD.
Get-AzureADUser -UserPrincipalName | Select DisplayName,AccountEnabled
Get-MsolUser -UserPrincipalName | Select-Object DisplayName,BlockCredential
If the AccountEnabled attribute is set to "False", you can check also this via Graph API (https://developer.microsoft.com/en-us/graph/graph-explorer)
1) Log in to the graph explorer with a Global Admin account by clicking the "Sign in with Microsoft" button.
2) Make a GET call > https://graph.microsoft.com/beta/users/USERNAME@YOUR_TENANT.onmicrosoft.com?$select=accountEnabled
If you want to fetch this information about all users in your tenant, you can use https://graph.microsoft.com/beta/users?$select=displayname,accountEnabled