Using SharePointPnP.PowerShell modules.

SharePoint Online - Bulk add items to list.ps1

# variables
$siteURL = "https://org.sharepoint.com/sites/siteName"
$sharePointAdminUser = 'admin@org.onmicrosoft.com'
$cred = Get-Credential -UserName $sharePointAdminUser -Message 'Connect with a user with global level permissions'

# connect
Connect-PnPOnline -Url $siteURL -Credentials $cred

# Import values from CSV
$path = ".\source.csv"
$rows = Import-Csv $path 

# loop thru lines in CSV file 
ForEach ($row in $rows) { 
    $val1 = $row.ColumnTitle1
    #
    #
    $valN = $row.ColumnTitleN
    
    Add-PnPListItem -List "List Name" `
                    -Values @{
                          "ColumnIdentifier1" = "$val1"; 
                          "ColumnIdentifier2" = "$val2" 
                          }
}