在这里

https://blog.areflyen.no/2017/06/18/problem-with-connecting-to-sharepoint-online-in-office-365-with-powershell-sharepoint-designer-and-other-3 -party-tools/

Does anyone know if it is possible to connect to SharePoint online via Client Side Object Model from PowerShell when Legacy Auth is disabled?  When  the legacy protocols are disabled I get this error trying to create a client context:

Failed to connect to (site), Exception calling "ExecuteQuery" with "0" argument(s): "Cannot contact web site (site) or the web site does not support SharePoint Online credentials. The response status code is 'Unauthorized'. The response headers are 'X-SharePointHealthScore=0, X-MSDAVEXT_Error=917656; Access+denied.+Before+opening+files+in+this+location%2c+you+must+first+browse+to+the+web+site+and+select+the+option+to+login+automatically.

Here's how I make the connection, which works fine with legacy authentication protocols enabled:

    [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint.Client")

    $ccCtx = New-Object microsoft.sharepoint.client.clientcontext($Sitename)
     $ccCtx.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($UserName, $Password)
     $ccCtx.ExecuteQuery()

Here you go

https://blog.areflyen.no/2017/06/18/problem-with-connecting-to-sharepoint-online-in-office-365-with-powershell-sharepoint-designer-and-other-3-party-tools/