Purchased an 6700 XT while out in the states but was paid for by my brother in law. I’m back in the UK with the card and receipt- is the warranty still valid and could I RMA it in the UK (if needed obviously)?
Assuming this is an AMD Ref. design, not one of the partner design models.
If it was purchased through the AMD Store (online), you will have to ship it back to the bro. in law and get him to put in a warranty claim. All details will be under his name/address.
If it was purchased from a retail store (with in law details), then you are considered 2nd owner (no warranty), so posting back to U.S. looks like only option.