Hi @mdh,
Thanks for sharing your question with us!
Yes, I do think it would be best practice to either take done products that won’t ever be available again if possible to foster a good user experience. At the moment, yes I do think you let those users know that the product they subscribed to is not going to be available again via the back in stock flow they are already subscribed to and show products that are similar that they might be interested in is a great idea!
However, as those products will be taken done, unless for some reason they can’t be and if so please share that with me, then you won’t need to tag the products, however, tagging products is a great idea for any future strategies you might have.
Thanks for partipcation in the Community!
-Taylor