Hello SharePointers,

Below is the Sharepoint code to switch back to  Classic Document Library  Experience from Modern library experience using Powershell.

Add-Type -Path “C:\Program Files\SharePoint Online Management Shell\Microsoft.Online.SharePoint.PowerShell\Microsoft.SharePoint.Client.dll”
Add-Type -Path “C:\Program Files\SharePoint Online Management Shell\Microsoft.Online.SharePoint.PowerShell\Microsoft.SharePoint.Client.Runtime.dll”
$MyCredentials = Get-Credential
Connect-SPOService -Url https://mylab-admin.sharepoint.com -credential $MyCredentials
$webUrl = ‘https://mylab-sharepoint.com/sites/’
[Microsoft.SharePoint.Client.ClientContext]$clientContext = New-Object Microsoft.SharePoint.Client.ClientContext($webUrl)
$clientContext.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($MyCredentials.UserName,$MyCredentials.Password)
$site = $clientContext.Site;
$clientContext.load($site);
$sitefeatureguid = new-object System.Guid “E3540C7D-6BEA-403C-A224-1A12EAFEE4C4”
$site.Features.Add($sitefeatureguid, $true, [Microsoft.SharePoint.Client.FeatureDefinitionScope]::None);
$clientContext.ExecuteQuery();

Happy SharePointing Folks!Hope it helps!!