Connect to SharePoint Online using CSOM DLLs (Legacy method)

Microsoft-SPO-Connect.ps1

$username = "username@tenant.onmicrosoft.com" 
$securePassword = Read-Host -Prompt "Enter password" -AsSecureString
$SecurePassword = $securePassword | ConvertTo-SecureString -AsPlainText -Force

Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.dll" 
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Runtime.dll" 
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Taxonomy.dll" 

function Connect-SPO{
    Param(
        [string] $url
    )

    $clientContext = New-Object Microsoft.SharePoint.Client.ClientContext($url) 
    $credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($username, $securePassword) 
    $clientContext.Credentials = $credentials 

    if (!$clientContext.ServerObjectIsNull.Value){ 
        Write-Host "Connected to SharePoint Online site: '$Url'"
        return $clientContext
    }else{
        Write-Host "Client context not available." -ForegroundColor Red
        break
    }

}

$clientContext = Connect-SPO -url "https://tenant.sharepoint.com/"

$web = $clientContext.Web
$clientContext.Load($web)
$clientContext.ExecuteQuery()

Write-Host "Processing web with URL: '$($web.Url)'"