SharePoint Online: Add Content Type to List or Document Library using PowerShell

#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 Add-ContentTypeToList()
{ 
    param
    (
        [Parameter(Mandatory=$true)] [string] $SiteURL,
        [Parameter(Mandatory=$true)] [string] $ListName,
        [Parameter(Mandatory=$true)] [string] $CTypeName
    )

    Try {
        $Cred= Get-Credential
        $Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.Username, $Cred.Password)

        #Setup the context
        $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
        $Ctx.Credentials = $Credentials
        
        #Get the List
        $List = $Ctx.web.Lists.GetByTitle($ListName)
        $Ctx.Load($List)
        $Ctx.ExecuteQuery()
        
        #Enable managemnt of content type in list - if its not enabled already
        If($List.ContentTypesEnabled -ne $True)
        {
            $List.ContentTypesEnabled = $True
            $List.Update()
            $Ctx.ExecuteQuery()
            Write-host "Content Types Enabled in the List!" -f Yellow
        }

        #Get all existing content types of the list
        $ListContentTypes = $List.ContentTypes
        $Ctx.Load($ListContentTypes)

        #Get the content type to Add to list
        $ContentTypeColl = $Ctx.Web.ContentTypes
        $Ctx.Load($ContentTypeColl)
        $Ctx.ExecuteQuery()
        
        #Check if the content type exists in the site        
        $CTypeToAdd = $ContentTypeColl | Where {$_.Name -eq $CTypeName}
        If($CTypeToAdd -eq $Null)
        { 
            Write-host "Content Type '$CTypeName' doesn't exists in  '$SiteURL'" -f Yellow
            Return 
        }

        #Check if content type added to the list already
        $ListContentType = $ListContentTypes | Where {$_.Name -eq $CTypeName}
        If($ListContentType -ne $Null)
        {
            Write-host "Content type '$CTypeName' already exists in the List!" -ForegroundColor Yellow
        }
        else
        {
            #Add content Type to the list or library
            $AddedCtype = $List.ContentTypes.AddExistingContentType($CTypeToAdd)
            $Ctx.ExecuteQuery()
           
            Write-host "Content Type '$CTypeName' Added to '$ListName' Successfully!" -ForegroundColor Green
        }
   }
    Catch {
        write-host -f Red "Error Adding Content Type to the List!" $_.Exception.Message
    } 
}

#Set parameter values
$SiteURL="https://crescent.sharepoint.com"
$ListName="Project Frosty"
$CTypeName="Project Template"

#Call the function
Add-ContentTypeToList -SiteURL $SiteURL -ListName $ListName -CTypeName $CTypeName

#Config Variables
$SiteURL = "https://Crescent.sharepoint.com/sites/marketing"
$ContentTypeName="Crescent Invoice Template V2"
$ListName="Invoices"

#Get Credentials to connect
$Cred = Get-Credential

#Connect to PnP Online
Connect-PnPOnline -Url $SiteURL -Credentials $Cred
    
#Get the content type
$ContentType = Get-PnPContentType -Identity $ContentTypeName

If($ContentType)
{
    #Add Content Type to Library
    Add-PnPContentTypeToList -List $ListName -ContentType $ContentType
}
else
{
    Write-host -f Yellow "Could Not Find Content Type:"$ContentTypeName
}

#Parameters
$SiteURL = "https://crescent.sharepoint.com/sites/Purchase"
$ListName = "Site Pages"
$ContentTypeName = "Site Page"

Try {
    #Connect to SharePoint Online site
    Connect-PnPOnline -Url $SiteURL -UseWebLogin

    #Get the context
    $Ctx = Get-PnPContext

    #Check if the List or Library Exists
    $List = Get-PnPList -Identity $ListName
    If($List -ne $Null)
    {
        #Add Content type to the list
        $ContentType = Get-PnPContentType -Identity $ContentTypeName
        If($ContentType)
        {
            #Check if the List has the content type already
            $ListContentType = Get-PnPContentType -List $ListName -Identity $ContentTypeName -ErrorAction SilentlyContinue
            If(!$ListContentType)
            {
                #Add Content Type to List
                Add-PnPContentTypeToList -List $ListName -ContentType $ContentType
                Write-host  -f Green "'$ContentTypeName' content type added to the List '$ListName'"
            }
            Else
            {
                Write-host -f yellow "'$ContentTypeName' content type already exists in the List!"
            }
        }
        Else
        {
            Write-host -f Yellow "Could Not Find the '$ContentTypeName' Content Type!"
        }
    }
    Else
    {
        Write-Host -f Yellow "List '$ListName' does not exist!"
    }
}
Catch {
    Write-host -f Red "Error:" $_.Exception.Message
}