SharePoint Online: Download Attachments from List using PowerShell

Requirement: Download attachments from SharePoint Online List

PowerShell to download attachments from a List Item:
Lets download SharePoint list item attachment programmaticallyfrom a particular list item.

#Load SharePoint CSOM Assemblies
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"

Function Download-ListItemAttachments()
{
    param
    (
        [Parameter(Mandatory=$true)] [string] $SiteURL,
        [Parameter(Mandatory=$true)] [string] $ListName,
        [Parameter(Mandatory=$true)] [string] $ListItemID,
        [Parameter(Mandatory=$true)] [string] $DownloadPath
    )    
   Try {
        #Setup Credentials to connect
        $Cred = Get-Credential
        $Cred = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.UserName,$Cred.Password)

        #Setup the context
        $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
        $Ctx.Credentials = $Cred

        #Get the List Item
        $List = $Ctx.Web.Lists.GetByTitle($ListName)
        $ListItem= $List.GetItemByID($ListItemID)

        #Get All attachments from the List Item
        $AttachmentsColl = $ListItem.AttachmentFiles
        $Ctx.Load($AttachmentsColl)
        $Ctx.ExecuteQuery()

        #Get each attachment
        ForEach($Attachment in $AttachmentsColl)
        {
            #Download attachment
            $FileContent = [Microsoft.SharePoint.Client.File]::OpenBinaryDirect($Ctx, $Attachment.ServerRelativeUrl)
            $FileStream = [System.IO.File]::Create($DownloadPath+$Attachment.FileName)
            $FileContent.Stream.CopyTo($FileStream)
            $FileStream.Close()
       }

        write-host  -f Green "Total List Attachments Downloaded : $($AttachmentsColl.count)"
    }
    Catch {
        write-host -f Red "Error Downloading List Item Attachments!" $_.Exception.Message
    } 
}

#Set Parameters
$SiteURL= "https://crescent.sharepoint.com/"
$ListName="Projects"
$ListItemID="1"
$DownloadPath="C:\Temp\"

#Call the function to copy list items
Download-ListItemAttachments -SiteURL $SiteURL -ListName $ListName -ListItemID $ListItemID -DownloadPath $DownloadPath

Download Attachments from All Items in the List using PowerShell:
Here is the PowerShell to download SharePoint Online list attachments from all items.

#Load SharePoint CSOM Assemblies
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"

Function Download-ListAttachments()
{
    param
    (
        [Parameter(Mandatory=$true)] [string] $SiteURL,
        [Parameter(Mandatory=$true)] [string] $ListName,
        [Parameter(Mandatory=$true)] [string] $DownloadDirectory
    )    
   Try {
        #Setup Credentials to connect
        $Cred = Get-Credential
        $Cred = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.UserName,$Cred.Password)

        #Setup the context
        $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
        $Ctx.Credentials = $Cred

        #Get All Items from the List
        $List = $Ctx.Web.Lists.GetByTitle($ListName)
        $ListItems = $List.GetItems([Microsoft.SharePoint.Client.CamlQuery]::CreateAllItemsQuery())
        $Ctx.Load($ListItems)
        $Ctx.ExecuteQuery()

        #Create download directory if it doesn't exist
        If (!(Test-Path -path $DownloadDirectory))        
        {            
            New-Item $DownloadDirectory -type directory          
        }

        #Iterate through each list item
        Foreach($Item in $ListItems)
        {
            #Get All attachments from the List Item
            $AttachmentsColl = $Item.AttachmentFiles
            $Ctx.Load($AttachmentsColl)
            $Ctx.ExecuteQuery()

            #Get attachment for each list item
            ForEach($Attachment in $AttachmentsColl)
            {
                #Download attachment
                $FileContent = [Microsoft.SharePoint.Client.File]::OpenBinaryDirect($Ctx, $Attachment.ServerRelativeUrl)
                $FileName= $DownloadDirectory+$Item.id.ToString()+"_"+$Attachment.FileName
                $FileStream = [System.IO.File]::Create($FileName)
                $FileContent.Stream.CopyTo($FileStream)
                $FileStream.Close()
           }
        }

        write-host  -f Green "List Attachments Downloaded Successfully!"
    }
    Catch {
        write-host -f Red "Error Downloading List Attachments!" $_.Exception.Message
    } 
}

#Set Parameters
$SiteURL= "https://crescent.sharepoint.com/"
$ListName="Projects"
$DownloadDirectory="C:\Temp\"

#Call the function to copy list items
Download-ListAttachments -SiteURL $SiteURL -ListName $ListName -DownloadDirectory $DownloadDirectory