Shows all M365 group connected sites and reports if the associated M365 group exists.

Find-OrphanedM365Groups.ps1

#requires -module "PnP.PowerShell"

# Required permissions:	
#   Microsoft Graph API : One of Directory.Read.All, Directory.ReadWrite.All, Group.Read.All, Group.ReadWrite.All, GroupMember.Read.All, GroupMember.ReadWrite.All	
#   SharePoint Online : Sites.FullControl.All
Connect-PnPOnline `
            -Url         "https://$env:O365_TENANT-admin.sharepoint.com" `
            -ClientId    $env:O365_CLIENTID `
            -Thumbprint  $env:O365_THUMBPRINT `
            -Tenant      $env:O365_TENANTID `
            -ErrorAction Stop

$sites = Get-PnPTenantSite -GroupIdDefined $true -ErrorAction Stop

$results = foreach( $site in $sites )
{
    Write-Host "[$(Get-date)] - Scanning site: $($site.Url)"

    if( $site.GroupId -ne [Guid]::Empty )
    {
        $groupId = $site.GroupId
    }
    else
    {
        $groupId = $site.RelatedGroupId
    }

    try
    {
        $group = Get-PnPMicrosoft365Group -Identity $groupId -ErrorAction Stop
    }
    catch
    {
        Write-Error "Failed to lookup group: $groupId. Error: $_"
    }

    [PSCustomObject] @{
        SiteUrl        = $site.Url
        GroupId        = $site.GroupId
        RelatedGroupId = $site.RelatedGroupId
        GroupExists    = $null -ne $group
    }
}

$results | Export-Csv -Path "M365GroupConnectionExists.csv" -NoTypeInformation