SharePoint Online: Update Multiple Lines Of Text Field Value using PowerShell

Requirement: Update Multiple lines of text field value in SharePoint Online using PowerShell.

PowerShell to Set Multiline text field in SharePoint Online:
I've a column called "Project Description" of "Plain text" type in "Projects" list and here is the CSOM PowerShell script to update multiple lines of text field value in SharePoint Online.

#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"
 
#Parameters
$SiteURL = "https://CrescentIntranet.sharepoint.com/sites/PMO"
$ListName ="Projects"
$FieldName = "Project_x0020_Description"
$ItemID = 1

#Get credentials to connect
$Cred = Get-Credential

Try {
    #Setup the Context
    $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
    $Ctx.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.UserName, $Cred.Password)
 
    #Get the List Item to update
    $List = $Ctx.Web.Lists.GetByTitle($ListName)
    $ListItem = $List.GetItemById($ItemID)
    $Ctx.Load($ListItem)
    $Ctx.ExecuteQuery()
 
    #Update Multiple lines of text Field value
    $ListItem[$FieldName] = "Project Started: Q1 2018"+[System.Environment]::NewLine+"Completion Goal: Q2 2018"
    $ListItem.Update()
    $Ctx.ExecuteQuery()
    Write-host -f Green "Multiple Lines of Text Field Value has been updated for the list Item!"
    }
Catch {
    write-host -f Red "Error:" $_.Exception.Message    
}

Here is how it looks like in SharePoint Online:

PnP PowerShell to Update Multiple Lines of Text Column Value
If your column is set to allow Rich text or or Enhanced rich text, Here is how to update multi-lines of text field value with PnP PowerShell:

#Config Variables
$SiteURL = "https://CrescentIntranet.sharepoint.com/sites/PMO"
$ListName = "Projects"
$ItemID = 1
 
#Connect to PnP Online
Connect-PnPOnline -Url $SiteURL -UseWebLogin
 
#Update multiple lines of value using PowerShell
Set-PnPListItem -List $ListName -Identity $ItemID -Values @{"Project_x0020_Description"= "Project Started: Q1 2018 
Completion Goal: Q2 2018"}