Unless otherwise stated, you can use Rabble in any store that sells the product, including online stores. Just remember to always save the receipt!
However, please keep the following in mind:
Store-specific offers: If an offer explicitly states that it is only valid at specific stores, you must purchase the product from one of those listed retailers to receive your cashback.
Suggested stores: If stores are listed on the offer without any strict restrictions, they are simply suggestions for where you are most likely to find the product in stock.
Country restrictions: The receipt must always come from the same market as the one you are using the app in. For example, if you are using Rabble in Sweden, the receipt must be from a Swedish store.