List all users' last login date

JakobRohde this is a classic Microsoft 365 housekeeping task and question. A pity Microsoft is not offering something out of the box.

I would suggest following Powershell script, which returns not only your users last login date as CSV file, but also assigned licenses. This way you may check whether there is someone not logging in and consuming licenses.

Install-Module AzureADPreview -AllowClobber -Force

Connect-AzureAD

$usersexport = [system.collections.arraylist]@()

Get-AzureADUser | % {
    $User = $_
    $UPN = $User.UserPrincipalName
    
    Write-Output "Start analysing $UPN"

    $LoginTime = Get-AzureAdAuditSigninLogs -top 1 -filter "userprincipalname eq '$UPN'" | select CreatedDateTime
    $Licenses = Get-AzureADUserLicenseDetail -ObjectId $User.ObjectId | % { $_.ServicePlans | Where {$_.AppliesTo -eq "User"}} | select -ExpandProperty ServicePlanName
    
    $Export = [pscustomobject]@{
        'DisplayName' = $User.DisplayName; 
        'UserPrincipalName' = $UPN;
        'LastSignInDate' = $LoginTime.CreatedDateTime;
        'Licenses' = $Licenses -join ",";
    }
    
    $usersexport.Add($Export)
    
    Write-Output $Export
}
$usersexport | Export-CSV $Home\LastLogonDate.csv