I remember filing a similar issue for this a long time ago, but the issue is still there with his command. Invalid identity for URI for Remove-AzsAzureBridgeDownloadedProduct is caused by the ProductResource object being piped to Remove-AzsAzureBridgeDownloadedProduct:
$azMktplaceVersion | Remove-AzsAzureBridgeDownloadedProduct
Here is the error:
Remove-AzsAzureBridgeDownloadedProduct_DeleteViaIdentity: Invalid identity for URI '/subscriptions/{subscriptionId}/resourcegroups/{resourceGroupName}/providers/Microsoft.AzureBridge.Admin/activations/{activationName}/downloadedProducts/{productName}'
I believe this is caused by the fact that productName has "Default/" in the name, when the official name should be what follows "Default/".