Yes, multi-currency setup is one of the significant limitations of Shopify for post-purchase apps, impacting offer rendering for the customer.
If a customer places an order in a non-native store currency (for example, if your native store currency is USD and the customer places an order in EUR), Shopify will not render the offer for this order.
Is there any workaround for this limitation?
Unfortunately, no. It's a global limitation by Shopify for all post-purchase apps, without any workarounds.