Rough proof of concept on locating transcript files stored in OD4B.

Get-TranscriptFile.ps1

#requires -modules "PnP.PowerShell"

function Get-TranscriptFile
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory=$true)]
        [DateTime]
        $CreatedOnOrBefore
    )

    begin
    {
        $context = Get-PnPContext
    }
    process
    {
        $library = Get-PnPList -Identity "Documents" -ErrorAction Stop

        $camlQuery = [Microsoft.SharePoint.Client.CamlQuery]::CreateAllItemsQuery()
        $camlQuery.ListItemCollectionPosition = $null
        $camlQuery.FolderServerRelativeUrl    = "$($library.RootFolder.ServerRelativeUrl)/Teams Meeting Transcripts"

        do
        {
            $batch = $library.GetItems( $camlQuery )
            $library.Context.Load($batch)

            Invoke-PnPQuery

            $batch | Select-Object Id, 
                                   @{Name="FileName";   Expression={ $_.FieldValues.FileLeafRef }}, 
                                   @{Name="FilePath";   Expression={ $_.FieldValues.FileDirRef }}, 
                                   @{Name="CreateDate"; Expression={ $_.FieldValues.Created }}

            $camlQuery.ListItemCollectionPosition = $batch.ListItemCollectionPosition
        }
        while( $null -ne $camlQuery.ListItemCollectionPosition )
    }
    end
    {
    }
}

# requires SharePoint > Application > Sites.Manage.All
Connect-PnPOnline `
      -Url        "https://$env:O365_TENANT-admin.sharepoint.com" `
      -ClientId   $env:O365_CLIENTID `
      -Thumbprint $env:O365_THUMBPRINT `
      -Tenant     $env:O365_TENANTID

$sites = Get-PnPTenantSite -IncludeOneDriveSites | Where-Object -Property Template -match "^SPSPERS"

foreach( $site in $sites )
{
    # requires SharePoint > Application > Sites.Read.All
    Connect-PnPOnline `
        -Url        $site.Url`
        -ClientId   $env:O365_CLIENTID `
        -Thumbprint $env:O365_THUMBPRINT `
        -Tenant     $env:O365_TENANTID

    $transcripts = Get-TranscriptFile -CreatedOnOrBefore ([DateTime]::Today.AddDays(-60))

    $transcripts
}